AU2006200265A1 - Screening for blood coagulation defects using metal ions - Google Patents

Description

P/00/01 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT

(ORIGINAL)

Name of Applicant: Instrumentation Laboratory of Viale Monza 338, Milan 1-20128, ITALY Actual Inventor: ROSEN, Bert Steffen HALL, Christina Maria Yvonne Address for Service: Invention Title: DAVIES COLLISON CAVE, Patent Trademark Attorneys, of 1 Nicholson Street, Melbourne, 3000, Victoria, Australia Ph: 03 9254 2777 Fax: 03 9254 2770 Attorney Code: DM "Screening for blood coagulation defects using metal ions" The following statement is a full description of this invention, including the best method of performing it known to us:- SCREENING FOR BLOOD COAGULATION DEFECTS USING METAL IONS This application is a divisional of Australian Patent Application No. 2003212064, the entire content of which is incorporated herein by reference.

Description Field of the Invention The present invention relates to in vitro photometric methods, kits and reagents for qualitative screening and quantitative determination of 0 the functional activity of components of the Protein C anticoagulant pathway of blood coagulation, comprising measuring the conversion rate of an exogenous substrate by an enzyme, the activity of which is related to the Protein C anticoagulant activity, in a blood sample of a human comprising coagulation factors and said exogenous substrate after at least partial activation of coagulation through the intrinsic, extrinsic or common pathway and triggering coagulation by adding calcium ions; and comparing said conversion rate with the conversion rate of a normal human blood sample determined in the same way, Background of the Invention Maintenance of a proper hemostasis is the result of a careful balance between pro- and anticoagulant activities. After a trauma, coagulation is triggered primarily through activation of coagulation Factors IX and X (FIX, FX) by tissue factor (also denoted tissue thromboplastin) and Factor VII -2- 1 (FVII) followed by generation of thrombin, which in turn cleaves fibrinogen to form soluble fibrin. After crosslinking by Factor XIII, a three-dimension.

al insoluble gel clot is obtained which prevents further blood losses.

Regulation of this highly potent system shown schematically in Figure 1 of the drawings is accomplished bya balanced relation between procoagulant events (shown with solid line arrows) and anticoagulant events (shown with dashed line arrows). The anticoagulant events comprise 1) inhibition of already formed thrombin by antithrombin (AT) and a2-macroglobulin and 2) prevention of further thrombin formation by the Protein

C

anticoagulant pathway. Here, activated Protein C (APC) inactivates the coagulation proteins Factor VIII and Factor Vin their activated forms (FVIIIa, FVa) through proteolytic cleavage. In addition inhibition of generated Fac- tor Xa is also accomplished by antithrombin and tissue factor pathway inhibitor (TFPI). the latter also inhibiting the tissue factor/Factor VIIa complex. Factor Villa and Factor Va act as cofactors in the activation of Factor

X

andprothrombin, respectively, and increase the reaction rates of these processes about 1000-fold each. Thus, these cofactors act as potent stimulators of the coagulation. Their inactivation by APC therefore essentially stops further thrombin generation, thus providing a strong anticoagulant effect. Protein S and also Factor V act as cofactors to activated Protein

C

(APC).

As shown in Figure 1. the activation of coagulation through the intrinsic or extrinsic systenis results in the activation of Factor X. a key component in the final common pathway. In the intrinsic system, the initial event is the activation of contact factors (Factor XII. prekallikrein) followed by the activation of Factor XI, which in turn activates Factor IX. In the extrinsic system, Factor IX and Factor X are activated by the tissue factor/Factor Vila complex.

As Figure 1 as well shows, calcium ions have to be present in several of these reactions. The activation of Factor X by Factor IXa and ofprothrombin by Factor Xa requires procoagulant phospholipids. In vivo. this is provided -3by the membrane surface of activated platelets; in vitro byplatelet extracts, purified phospolipids, synthetic phospoliplds and/or crude phospholipid extracts from suitable sources. The total and free calcium Ion concentra.

tion in native plasma is about 2.4 and and 1.2 mmol/L. respectively. Typically, calcium ion concentrations used in analytical methods for determi.

nation of coagulation or anticoagulation factors are in the range 1.5 mmol/L. The concentrations of other metal ions in plasma are lower, typical values for total concentration being 1 mmol/L for Mg 2 and 5 40 lmol/L for Zn 2 Cu 2 and Mn2+.

Defects in the Protein C anticoagulant pathway may cause a risk of thrombosis due to a decreased capacity to prevent thrombin formation.

Such defects may be due to deficiencies in the activity of Protein C and/or Its cofaetor Protein S. Another recently detected defect is a point mutation in the Factor V gene A) at nucleotide 1691, resulting in the amino acid substitution Arg Gln at position 506 in Factor V/Factor Va, denoted FV: 5 0 6 or Factor V Leiden. Heterozygosity and homozygosity for this mutation are often denoted FV:R506Q and FV:9506Q, respectively. This mutation is at one of the three APC cleavage sites (amino acids 306, 506, 679) in Factor Va, which confers an impairment of ts degradation by activated Protein C (APC), denoted APC resistance.

APC resistance is to be considered a blood coagulation disorder recognized by an abnormally low anticoagulant response to activated Protein

C

(APC) and the determination of said APC resistance may be used to screen for and diagnose thromboembolic diseases, such as hereditary thrombophilia or for determining the risk for a human to acquire a manifestation of this blood coagulation disorder (DahlbAck B, EP-608 235).

Hence, there is a need to investigate these components of the Protein

C

anticoagulant pathway in the evaluation of thrombotic patients and potentially also to screen for abnormalities of Protein C, Protein S and Factor

V

anticoagulant activity in situations connected with an increased risk of thrombosis such as before surgery, during trauma and during pregnancy or -4in connection with the use of oral contraceptive pills or hormone replacement therapy. Currently. clotting and/or chromogenic assays are available for analysis of Protein C and Protein S activity as well as for the detection of APC resistance, which to at least 90% is due to the Factor Vmutation at po- 5 sition 506.

Protein C activity is typically measured after activation of the endogenous Protein C, contained in a plasma sample, by thrombin or by a snake venom enzyme from Agkistrodon contortrix contortrix (Stocker K. EP 203 509), commercially available as the reagent Protac®C (Pentapharm

AG,

Basel, Switzerland). The concentration of Protac@C in the activation mixtureis typically about 0.1 U/mL or above since otherwise an insufficient activation of Protein C may be obtained (Martinoli J. Stocker K.Thromb Res 43. 253,264 (1986); Mc Call F et al.Thromb Res 45, 681-685 (1.987)).

After activation by Protac®C, the protein C activity is determined with a clotting or chromogenic assay (Bertlna R. Res Clin Lab. 20, 127-138 (1990); Marlar R, Adcock DM. Hum Pathol 20. 1040-1047 (1989), Rosen

S.

EP 486 515). In clotting methods. coagulation is triggered through the intrinsic pathway by using APTT reagents or through the extrinsic pathway with the use of tissue factor. In both cases calcium ions are added to a final concentration of usually 5-10 mmol/L. Commercial kits and reagents are available for determination of Protein C activity such as Acticlot C (American Diagnostica), Stachrom Protein C (Diagnostica Stago). Staclot Protein C (Diagnostica Stago), CoamaticO Protein C (Chromogenix AB) and Protein C Activator (Behring Diagnostica).

The activation of Protein C by thrombin is stimulated about 1000-fold by thrombomodulin, an endothelial cell membrane protein (Esmon CT and Owen WG. Proc Natl Acad Scd 78, 2249-2252 (1981)). The use of thrombin/thrombomodulin as activator of Protein C for analysis of Protein

C

and/or Protein S activity in plasma samples, utilizing a photometric method. is also known (Pittet J-L and Aiach M, FR Pat Appl. 2689 640-A1).

Protein S activity is determined from its stimulation of the activity of APO in its degradation of Factor Va and/or Factor Villa. Typically, in such assays a standardized amount of APC is added to a plasma sample or activation of endogenous protein C is performed Whereafter the clotting time is determined after a simultaneous or separate coagulation activation via the intrinsic system using an APTT reagent, via the extrinsic system using tissue factor or by Factor Xa (Bertina R, loc cit Preda L et al.Thromb Res 19-32 (1990): D'Angelo S et al. Thrornb Res 77. 375-378 (1995)). Chroino.

genic activity assays for protein S have also been published, utilizing Factor M~a as activator and monitoring Factor Xa generation (van de Waart

P,

Woodharns BJ. EP 567 636) or thrombin generation (Rosen S. EP'486515).

In all these methods calcium ions are added as mentioned above.

The Factor V mutation (FV:g 506) mutation in the Factor V molecule may be-detected with molecular- biology methods based upon the use of the polymerase chain reaction (PCR) technique (Bertina RM et al, Nature 369, 64-67 (1994)) or by methods in which the functional activity of A.PC Is determined.. Such activity methods may be co agulation-.based (Dahlbdck B. EP 608 235 Rosdn et al. Tftromb Iiaemost 72. 255-260 (1994)) anid include the use of predilution of sample plasma with a plasma with no or a low Factor V activity (Dahlb~ck B, EP-A-94 905 908.3 Jorquera JI et al. Lancet 344, 1162 -1163 (1994); Svensson PJ et al. Thromb Haernost 77, 332-335 (1997)). The latter assay principle. vz a coglto-ae assay using predilution of sample plasma is also utilized in a commiercial product, Coatest APC: Resistance V (Chromogenix AB). Alternatively, chromogenic methods may be used (Dahlick B, EP 608 235 Rosen et al,. Tlzrorb Haemost 73, 1364, Abstract 1778 (1995), Nicolaes GAF et al, Thromb Haemost 76, 404-410 (1996)).

Since genetic defects in the Protein C anticoagulant pathway are found in about 25% of unselected patients with venous thromboembolism (VTE) and in about 50% of patients with thrombophilia. i.e. patients from families with an Increased tendency to VTE, there is a need for a single test which detects all such abnormalities with a high sensitivity and specificity.

i.e. a global (overall) test. One concept for a global test is based upon the ac- -6- 1 tivation of Protein C in plasma with Protac®C and activation of coagulation via the intrinsic or extrinsic pathway (Bartl et al, USP 5,001,069: Kraus

M

EP-A- 696 642). Results obtained with a commercial kit application of this est, ProC Global (Behring Diagnostica, Marburg, Germany), in which intrinsic activation of coagulation is accomplished through addition of an APTT reagent, show a sensitivity for Protein C deficiency, Protein S deficiency and for FV:Q506 of, respectively, about 90%, 50-80% and more than on analysis of healthy individuals and thrombotic patients (Dati F et al, Clin Chem 43, 1719-1723 (1997); Ruzicka K et al.Thromb Res 87. 501-510 (1997)]. The specificity is about 50% in thrombotic cohorts (Dati F et al, oc cit i.e. a substantial proportion of positive results are obtained, which can not be linked to known defects in components in the Protein C anticoagulant pathway, such as in protein C, protein S and Factor V. Thus, this test lacks sufficient specificity.

Furthermore, results from analysis of pregnant women lacking any of the known defects in the Protein C anticoagulant pathway are clearly different from analysis of normal healthy individuals (RangArd B, Wagner C. Annals Hematol 74i Supplement II, Abstract 74. A77 (1997): Slegemund A et al, Annals Hematol 74: Supplement II, Abstract 188, A105 (1997)), which necessitates separate ranges for these cohorts. This as yet uncharacterized interference limits the general applicability of the test. An alternative global method for the detection of defects in the protein C anticoagulant pathway, based upon activation of endogenous plasmaProtein C byProtac C utilizes tissue factor as trigger of the coagulation (Preda L et al. Blood Coag Flbrinol 7, 465-469 (1996)). Also here, the sensitivity of the method is limted, especially for Protein S. Furthermore, different sample categories, e.g.

pregnant and non-pregnant women, may require different approaches for evaluation of the results due to interferences not only related to components in the Protein C anticoagulant pathway.

For a global test to be useful as a screening test for known inherited defects in the Protein C anticoagulant pathway, i.e. Protein C deficiency, protein S deficiency and the FV:g506 mutation, the sensitivity should be high. at least 90%, for all these defects. Furthermore the specificity should be high, above 6000. suitablY' above 700% and preferably above 80% in order to considerably reduce the number of false positive results' The state-ofthe-art methods do niot provide a satisfactory solution to these requiremnents. For the development of improved methods for the specific determi.

nation of Protein C and Protein S activity and for determination of mnutatbons in Factor V which affects its anticoagulant activity, it is also desirable to improve the resolution and specificity of these methods.

It is also desirable to improve the stability of different components used as separate reagents or as reagnts in kits conprising such methods.

Thus, the technical problem underlying the present Invention is the provision of in vitro methods with improved sensitivity and specificity for screening and for the specific detection of defects in the Protein C anticoagulant pathway of blood coagulation in a human. A further recognized prob lem Is to improve the stability of components in such methods.

Brief Description of the Invention It has now been unexcpectedly found that the addition of low levels of ions of divalent metals, such as Mg 2 Mn 2 Zn 2 t- N2+. Sr 2 Cu 2 ions or of the monovalent Cu+ Ion. in the presence of calciumlions enhances the anticoagulant activity of the Protein C anticoagulant pathway and provides for a high resolution between different levels of Protein C activity and Protein S activity, respectively, and a high discrimination for the presence of the FV:Q5o6 mutation, resulting in an improved sensitivity and specificity for detection of defects in components of the Protein C anticoagulant pathway with photometric and/or clotting methods. Thus, the invention also constitutes a new excellent global method for the Protein

C

anticoagulant pathway. In addition to that. divalent metal ions provide for an unexpected Improvement of the stability of the reagents used either when used separately or when used in test kits for determining the anticoagulant activity of components of the Protein C anticoagulant pathway in PAOPER:U Rgc\)33M9 divisioW doc431AM7AJ -8blood samples with photometric and/or clotting methods.

Subject-matter of the present invention thus is an in vitro photometric method for qualitative screening and quantitative determination of the functional activity of components of the Protein C anticoagulant pathway of blood coagulation, comprising measuring the conversion rate of an exogenous substrate by an enzyme, the activity of which is related to the Protein C anticoagulant activity, in a blood sample of a human comprising coagulation factors and said exogenous substrate after at least partial activation of coagulation through the intrinsic, extrinsic or common pathway and triggering coagulation by adding calcium ionsr and comparing said conversion rate with the conversion rate of a normal human blood sample determined in the same way, said method being characterized by adding further metal(s) ions to said sample.

In an embodiment of the invention there is thus provided an in vitro method for determining the functional activity of one or more components of the Protein C anticoagulant pathway of the blood coagulation. system,. comprising: providing a blood sample to be analyzed; activating the coagulation cascade by adding a procoagulant reagent to the blood sample to be analyzed; triggering coagulation by adding calcium ions to the blood sample; adding metal ions selected from the group consisting of Mg+2, Mn+2, Zn+2, Ni+2, Sr+2, Cu+2, or Cu+, ions at a concentration that increases the anticoagulant activity of one or more components of the Protein C anticoagulant pathway; incubating a reaction mixture comprising the components recited in steps observing clotting time; and P:OPERULi3(339l-W diviWm-Ldoc4nMl)3 -8Acomparing the clotting time for the blood sample to be analyzed with the clotting time for a normal blood sample as determined by the method recited in steps thereby allowing for determination of an activity of one or more components of the Protein C anticoagulant pathway.

The present invention is thus concerned with a novel in vitro method for screening for, in a human, defects in the Protein C anticoagulant pathway due to e.g. Protein C deficiency, Protein S deficiency and Factor V mutations such as the FV:Q506 mutation, or other Factor V defects related to APC resistance and/or APC cofactor activity. Such a method may be designed for the specific detection of either of Protein C deficiency-i Protein S deficiency or of mutations in Factor V/Factor Va which affect the cleavage rate by APC. One preferred embodiment of the present invention comprises a global test for the Protein C anticoagulant pathway.

The term "metal(s) ions" stands for the fact that ions of one or more of said further metals may be present. Preferred ions of said further metals are divalent metal ions or the ions of monovalent copper, such as Mg 2 Mn Zn Cu Ni 2 Sr, and/or Cu t ions.

The term "blood sample" is defined to cover a blood sample, such as -9- 1 whole blood, or a blood derived sample such as a blood plasma sample or a blood serum sample.

The term "photometric assay" is defined to cover colorimetric, fluorimetric and luminonietric assay methods.

The term "coagulation factors" stands for such factors comprising components in the intrinsic, extrinsic and common pathway (procoagulant events see Figure 1) and in the Protein C anticoagulant pathway (anticoagulant events see Figure 1) and being either solely endogenous, i.e. being inherent in the blood sample, or comprising also the addition of such exogenous factors. Furthermore. phospholipid(s) may be added in the method when utilizing any of the intrinsic, extrinsic or common pathway for activation of coagulation.

Said novel method will thus allow improved screening and diagnosing of defects in the Protein C anticoagulant pathway in investigation of patients with thromboembolic diseases such as deep venous thrombosis and/or pulmonary embolism. In case a patient belongs to a family with hereditary thrombophilia, said novel method is also suitable for investigation of family members of such a patient in order to determine the possible inheritance of defects within said pathway. Said novel method is also suitable for diagnosing of defects in the Protein C anticoagulant pathway in investigation of patients before surgery, patients with trauma or in pregnant women or in women receiving oral contraceptive pills or hormone replacement therapy such as oestrogen therapy. Furthermore, global methods may be designed to allow the detection of known defects and of hitherto unrecognized defects in the Protein C anticoagulant pathway. The invention may also allow the design of specific photometric and/or clotting methods for such as yet unrecognized defects in said pathway.

Any of the above methods encompasses monitoring of conversion of a photometric exogenous substrate for either Factor Xa or thrombin. containing as leaving group a chromophore, a fluorophore or a luminophore.

Examples of such photometrically measurable leaving groups are p-nitro- 10 1aniline (pNA, chroznophore) for use in colorimetric methods, e.g. naphu-jy.

laniine and coumarin derivatives such as methylcoumnarine. alninoisoph.

thalic acid and its derivatives (fluorophores) for use in fluorlmetric mnethods and e.g. isoluminolamide (lummnophore) for use in luminonietric inethods.

The invention is most unexpected in light of the present knowledge in the field which, in fact, teaches that several divalent Ions Increase the procoagulant activity of certain vitamin K-dependent coagulation factors in the presence of calcium Ions (see procoagulant events in Figure so that it could not be expected that the addition of such further metal(s) iorns could improve tests relating to the anticoagulant activity. specifically in the Protein C anticoagulant pathway Thus, it Is known that Mg 2 stimulates the activity of Factor IXa (Byrne et al. JEioI Chem 1980; 255: 1430-1435: Sekiya F et a-1. JBIoI Chem 1995; 270: 14325-1433 1; Sekiya F et al, JEBiol Chzem 1996; 271: 8541 8544; Morita T et al. Thromb Haemost 1997; 78. Supplement: 430, Abstract PS- 1755) and also enhances the activation rate of Factor IX by FX~a and tis..

sue factor (Sekiya F et al. loc sit.1995, loc cit 1996; Morita T et al.. loc cit), It was also shown that neither Protein C nor prothrombin. Factor VII and Factor X are responsive to Mg 2 (Sekiya F et al, loc cit 1995 Mg 2 has been shon t alo simlate the prothrombin activation by Factor Xa, phospholipid and calc ium ions (Prendergast FG and Mann KG, JB~oI Chem 1977; 252: 840-85 an effect which, however. may not be pronounced at calcium ion concentrations above I mmolfL (Sekiya F et al. loc cit 1995 Furthermore, it has been shown that Factor IX has a unique binding site for Mn 2 (Amphlett GW et al. JEiol Chem 1978; 253: 6774-6779), which site has been sugge sted to be Identical with the Mg 2 binding site (Sekiya F et al, oc cit 1995).

Mn 2 ions have also been shown to enhance the binding of Factor

IX

to procoagulant phospholipids in the presence of calcium or Sr 2 ions, the latter thus also having a procoagulant effect (Liebman et al. J Blol Chem 11 S1 1987; 262, 7605-7612).

I Furthermore, Mg 2 and Mn 2 ions have been shown to increase the amidolytic activity of Factor VIIa. i.e. the cleavage rate of low molecular weight synthetic peptide substrates (Butenas S et al, Biochemistry 1994; 33: 3449-3456; Persson E, Petersen LC, Eur J Blochem 1995; 234: 293- 300) whereas Zn 2 ions have been reported to have an inhibitory effect on the amidolytic activity of Factor Vila but no effect on the amidolytic activity of Factor Xa. thrombin or activated Protein C (Pedersen AH et al,Thromb Haemost 1991; 65: 528-534). Mn 2 ions have also been shown to substitute for calcium ions in the activation of Factor X by Russell Viper Venom enzyme, albeit providing a lower activation rate (Bajaj P et al. J Biol Chem 1977; 252: 4758-4761).

The knowledge in the field also teaches that divalent metal ions such as Zn 2 and Cu 2 stimulate the autoactivation of Factor XII. a non-vitamin K-dependent coagulation factor (Shore et al, Blochemistry 1987; 26: 2250- 2258; Bernardo MM et al. J Biol Chem 1993; 268: 12468-12476).

0 A further illustration that the present invention was unexpected is the knowledge which teaches that Mg2+ and Mn 2 stimulate the inhibition of APC by the two plasma protease inhibitors a2-macroglobulin and.plasmin inhibitor (Heeb MJ et al, JBiol Chem 1991; 266: 17606-17612). Thus, the addition of Mg 2 and Mn 2 under the conditions used results in a decreased anticoagulant activity of APC.

Therefore, the present invention providing an increased anticoagulant activity of the Protein C anticoagulant pathway through the use of metal(s) ions such as e.g. divalent metal ions or Cu+ in addition to calcium ions.

could not be derived or expected from the state-of-the-art knowledge in the field.

Brief Description of the Drawings and Detailed Description of the Invention 12- In.the following, the invention is disclosed more in detail making reference to the drawings enclosed, wherein: Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 shows a schematic representation of the blood coagulation system and its regulation; shows a graphic representation of the results obtained in Example 2. i.e. the effects of the metal ions in a chromogenic Protein C assay; shows a graphic representation of the effects obtained according to Example 5, namely the effect of Mg 2 and Mn 2 in a chromogenic Protein S assay; assembles in a graphic representation the results obtained according to the method disclosed in Example 8, i.e. the effect of metal ions on discrimination for Protein S deficiency and for FV:Q506 in a global Protein C pathway assay using Factor Xa as activator; shows a graphic representation of the effects obtained according to Example 12, namelythe effect ofMg 2 in a global chromogenic assay for the detection of Protein C deficiency. Protein S deficiency and for FV:9506 mutation using a recombinant tissue factor; represents a graphic representation of the effects obtained according to Example 13, namely the effect of Mn 2 on the determination of free Protein S activity in a chromogenic thrombin generation assay; shows a graphic representation of the effects obtained according to Example 14. namely the effect of Mg 2 and Mn 2 on the determination of Protein C activity in a chromogenic thrombin generation assay; and provides a graphic representation of the effects obtained according to Example 15, namely the effect of Mg 2 and Mn 2 on the detection of Protein

C

deficiency. Protein S deficiency and for FV:Q506 mu- Figure 6 Figure 7 Figure 8 13tation in a global chromogenic method for using a recombinant tissue factor as activator of coagulation and monitoring thrombin generation.

A preferred embodiment of the present invention thus covers a method for the global screening for defects in the Protein C anticoagulant pathway of blood coagulation in a human, comprising A) incubating a blood sample of said human comprising coagulation factors with: 1) an activator for the Protein C in said sample.

2) a suitable coagulation activator, 3) an exogenous synthetic substrate for either Factor Xa or thrombin comprising a photometrically measurable leaving group, 4 )calcium ions, and 5) said further metal(s) ions: B) determining the conversion rate of said exogenous substrate; and C) comparing said conversion rate with the conversion rate of normal human blood sample determined in the same way.

A further preferred embodiment of the present invention relates to a method for the determination of free Protein S activity, comprising: A) incubating said blood sample comprising coagulation factors with: 1) exogenous activated Protein C or exogenous Protein C together with an activator of Protein

C,

2) a suitable coagulation activator, 3) an exogenous synthetic substrate for either Factor Xa or thrombin comprising a photometrically measurable leaving group, 4) calcium ions. and 5) said further metal(s) ions; B) determining the conversion rate of said exogenous substrate; and C) comparing said conversion rate with the conversion rate of normal human blood sample determined in the same way.

14- 1 Another preferred embodiment of the present invention relates to a method for the determination of Protein C activity, comprising: A) incubating a blood sample of said human comprising coagulation factors with: 1) an activator for the Protein C in said sample, 2) a suitable coagulation activator, 3) an exogenous synthetic substrate for either Factor Xa or thrombin comprising a photometrically measurable leaving group, and 4) calcium ions, and 5) said further metal(s) ions; B) determining the conversion rate of said exogenous substrate: and C) comparing said conversion rate with the conversion rate of normal human blood sample determined in the same way.

A fourth further preferred embodiment of the present invention covers a method for screening for Factor V mutation(s) in a blood sample of said human, comprising: A) incubating a blood sample of said human comprising coagulation factors with: 1) exogenous activated Protein C. or exogenous Protein C together with an activator of Protein C, or an activator for endogenous Protein

C,

2) a suitable coagulation activator, 3) an exogenous synthetic substrate for either Factor Xa or thrombin comprising a photometrically measurable leaving group.

4 calcium ions, and said further metal(s) ions; B) determining the conversion rate of said exogenous substrate: and C) comparing said conversion rate with the conversion rate of normal human blood sample determined in the same way.

In the above preferred methods for global screening for defects in the Protein C anticoagulant pathway, for the determination of free Protein S activity or Protein C activity or for screening for Factor V mutation(s) such as I the FV:Q5o6 mutation in a blood sample, step A) comprises incubating 'the blood sample of said human comprising coagulation factors in the presence' of the added further metal(s) ions used according to the present invention' with 1) an activator for the Protein C in said sample to provide activation of endogenous Protein C. or exogenous activated Protein C or exogenous' Protein C together with an activator of Protein

C.

2) a suitable coagulation activator to provide at least partial activation of coagulation.

3) an exogenous synthetic substrate for either FactorXa or thrombin comprising a pho tometrIcally measurable leaving group to provide for monitoring Factor Xa or thrombin activity and 4) calcium ions to trigger coagulation.

These steps 1) to 4) can be performed separately and/or simultane-.

ously, i e. in different sequentWa combinations providing for so-called "onestage" to "four-stage" methods as follows: In a one-stage method all components necessary for performing steps 1) to 4) above are added simultaneously.

In two-stage methods a) the components for steps 1) and 2) may first be combined followed by simultaneous addition of the exogenous substrate with calcium ions and or b) all the components but for calcium ions M1-3)) may be added simultaneously, the addition of calcium Ions then comprising the second step,or c) the components for step 2) and 41 may be included simultaneously and step 3) be performed as a separate step.

In three-stage methods a) steps 1) and 2) are combined and steps 3) and 4) performed as separate steps, or b) steps 1) and 2) are performed as separate steps and steps 3) and 4) are performed simultaneously, or c) steps 2) and 3) are performed as separate steps, and steps 1) and 4) are performed simultaneously, or d) step 1) is performed as a separate step, steps 2) and 4) are performed simultaneously, followed by step 3).

16- 1 In four-stage methods steps 1) to 4)are performed as separate steps in the order as described or in any other different order.

All one-, two-, three- or four-stage methods may be used in chromogenic. fluorimetric and luminometric methods.

Other embodiments of the invention comprise clotting methods, utilizing activation through the intrinsic, extrinsic or common pathway.

For any method, said further metal(s) ions used according to the present invention may be added either initially or at a later stage to any of said reagents. In applications where endogenous Protein C is activated by a Protein C activator, such as in methods for Protein C activity and global methods for the Protein C anticoagulant pathway, one preferred mode of the invention is to include said further metal(s) ions in the Protein C activation step, for example when Protac®C is used as the Protein C activator.

Specifically, the invention concerns the addition of divalent metal ions or of the monovalent Cu+ ion in view of increasing the resolution between different levels of, respectively, Protein C activity and Protein S activity as well as providing a high discrimination for the presence of the

FV:Q

5 0 6 mutation, resulting in an improved sensitivity and specificity for detection of defects in components of the Protein C anticoagulant pathway of blood coagulation. The range of concentrations of metal ions within which the anticoagulant activity of the Protein C system is stimulated varies with respect to the actual metal ion. The optimal concentration for Mg 2 ions is considerably higher than that for other metal ions. The concentration range for metal ions other than Mg 2 comprises 1 Rmol/L 2mmol/L, suitably 5 400 tmol/L and preferably 10 80 .mol/L. For Mg 2 ions, the concentration range comprises 20 .mol/L 10 mmol/L. suitably 100 pmol/L 2 mmol/L and preferably 200 imol/L 1 mmol/L.

The counter ion should be selected in such a way to allow the above 17- 1 described available concentrations of metal ions. Suitable counter ions are mono-, di- and trivalent anions, preferably mono- and divalent anions, such as chloride, sulphate and nitrate anions. Metal ions could also be provided in form of a metal ion complex with protein(s) such as blood protein or on a solid surface such as a metal ion coated wall of a reaction vessel.

For any application of the invention, photometric methods are used for monitoring the anticoagulant activityof components in the Protein C anticoagulant pathway.

In photometric methods, synthetic substrates with colorimetric, fluorimetric or luminometric leaving groups are used, which substrates preferably should be selective for Factor Xa or for thrombin. Since the generation of Factor Xa and thrombin according to the invention is influenced by the Protein C anticoagulant activity in the reaction mixture, containing a test sample from an individual, the measurement of the conversion rate of said substrates by said enzymes is suitably performed for determination of said Protein C anticoagulant activity. The measurement of said conversion rate is suitably compared with the corresponding conversion rate obtained when using a normal human plasma pool as a test sample. The conversion rate may be measured kinetically, i.e. by monitoring the change in optical density (OD) versus time, expressed as e.g. AOD/min, or measured after a fixed incubation time, expressed as OD.

The determination of the conversion rate of synthetic substrates is performed with instruments suitable for monitoring the release of the leavinggroup from the actual substrate chosen. When the conversion rate Is determined in a microplate reader, it is suitable to perform readings in the so called dual wavelength mode in order to eliminate possible differences between microplate wells. In such readings, one wavelength is selected for detecting the release of the leaving group whereas the other wavelength is selected in a wavelength range where the released leaving group does not have any appreciable absorbance. When a colorimetric leaving group such as paranitroaniline (pNA) is chosen, a suitable dual wavelength reading is per- 18- 1formed at 405 and 490 nanometers, expressed as OD405-490nm- A further aspect of the invention is the use of diluted blood samples in said photometric methods in order to avoid interference of blood sample components in the test sample. The final concentration, I.e. the concentration in the sample the optical density of which is.determined, of sample may vary depending on the actual method used. For colorimetric methods said blood sample concentration may be below 10% and preferably below Any activator of endogenous Protein C may be used such as thrombin with or without thrombomodulin. both from human or non-human sources or being produced by recombinant technology as wild-type proteins or as modified polypeptides to provide the suitable functional property, or alternatively a snake venom enzyme which activates Protein C. Suitable snake venom enzymes are preferably selected from the Agkistrodon snake family and may be added as crude venom or in a purified state as the product Protac

O

C. Suitable snake venom enzymes may also be produced by recombinant technology as wild-type proteins or as modified polypeptides to provide the suitable functional property. The concentration of the Protein C activator may vary depending on the actual conditions used. Thus, for the activator Protac®C the concentration may vary between 1 x 10-3 and 1 U/mL, preferably 2 x 10-3 and 0.3 U/mL during the activation of Protein C in a global method for the Protein C anticoagulant pathway or in specific methods for Protein C and free Protein S activity or for a method for detection of mutations in Factor V/Factor Va which affect the cleavage rate by APC.

According to a further preferred embodiment of the present invention, the activation of Protein C in the blood sample precedes or occurs simultaneously with activation of coagulation.

In the methods of the present invention, a suitable activator of coagulation is being used. Such activators may be selected to activate the socalled intrinsic, extrinsic or common pathway.

19- 1 Activation through the intrinsic system may be accomplished with an APT reagent containing a suitable contact activator, or with the separate addition of a contact activator. As such activators of the intrinsic pathway, suitable compositions of phospholipids and contact activators may be used. As contact activators, ellagic acid, collagen or collagen related substances or various forms of silica (kaolin, micronized silica, colloidal silica) may be used. Alternatively Factor XIIa, Factor Xla or Factor IXa may be used in combination with phosphollpids as activators of the intrinsic pathway rather than using a contact activator. Optionally, components such as prothrombin. Factor VIII/Factor VIlla and Factor X may be added. Photometric substrates selective for Factor Xa or thrombin are used.

Activation through the extrinsic system may be accomplished by tissue fattor from human or non-human tissues or produced by recombinant technology as a wild-type protein or as a suitably modified polypeptide with or without the addition of Factor VII/Factor VIla. Alternatively, activation may be accomplished by Factor VIla in combination with said phosphollpids. Optionally, reagents such as prothrombin. Factor V/Va. Factor IX and Factor X may be added. Photometric substrates selective for FXa or thrombin are used.

Activation of the common pathway may be accomplished by addition of exogenous Factor Xa or by exogenous Factor Xin combination with an exogenous activator of Factor X, such as a snake venom enzyme, e.g. a snake venom enzyme from Russell Viperili. Alternatively, said exogenous activator of Factor X may be added for activation of endogenous Factor X. Optionally, prothrombin and/or Factor V/Va may be added. Photometric substrates selective for thrombin are used.

In theabove described modes of the at least partial activation of coagulation according to the intrinsic, extrinsic or common pathway phospholipids may be added as a mixture of synthetic phospholipids and/or purified phospholipids or as crude extracts from biological sources such as e.g.

brainplatelet, placenta, egg yolk or soybean.

1 Generally, interferences due to e.g. variable functional levels of components in the sample may be minimized by including a suitable amount of plasma deficient of the Protein C anticoagulant pathway component to be measured. Such plasmas may be deficient of e.g. Protein C, Protein S or Factor V. In case of a global method for the Protein C anticoagulant pathway, a plasma deficient of Protein C. Protein S and Factor Vmay be added.

In case of a method for Protein S activity or a method for detection of a Factor V mutation which affects the degradation of Factor V/Va byAPC. exogenous Protein C may be added as a plasma deficient of Protein S and Factor V, respectively.

SProtein S may be added in methods for Protein C activity or for detection of said mutation(s) in Factor

V.

In case of protein C and protein S methods. Factor V/Factor Va may also be added to minimize interference from mutated Factor V present in the sample, vz mutations which affect the degradation of Factor V/Va by APC.

The above-mentioned coagulation factors and components of the Protein C anticoagulant pathway, vz Factor XIIa, Factor XIa, Factor IX/IXa, Factor VIII/VIIIa. Factor VII/VIIa. Factor X/Xa, Factor V/Va. prothrombin.

Protein C/APC and Protein S are of human or non-human origin, suitably bovine or human origin. Said coagulation factors may also be produced by recombinant technology as wild-type or as modified polypeptides with suitable biological activity.

In order to prevent fibrin gel formation, a fibrin polymerization inhibitor may be added to the reaction mixture such as Gly-Pro-Arg-Pro.

In chromogenic methods, any chromogenic substrates for Factor Xa may be used, such as e.g. Benzoyl-IIe-Glu-Gly-Arg-pNA (S-2222, Chromogenix AB, Ml6ndal, Sweden), N-a-Z-D-Arg-Gly-Arg-pNA (S-2765. Chromo- -21 1 genix AB), CH3SO2-D-Leu-Gly-Arg-pNA (CBS 31.39. Stago Diagnostica) and MeO-CO-D-CHG-Gly-Arg-pNA (Spectrozyme Xa. American Diagnostica, Greenwich, USA). Correspondingly, any chromogenic substrates for thrombin may be used, e.g. H-D-Phe-Pip-Arg-pNA (S-2238, Chromogenix AB), pyroGlu-Pro-Arg-PNA (S-2366, Chromogenix AB), D-Ala-Pro-Arg-pNA (S-2846, Chromogenix AB), Z-D-Arg-Sarc-Arg-pNA (S-2796. Chromogenix AB), AcOH*H-D-CHG.But-Arg-pNA (CBS 34.47, Stago) and H-D-HHT-Ala- S Arg-pNA (Spectrozyme TH, American Diagnostica).

A further subject matter of the present invention is a kit for use in the the above methods comprising the following components: a) an activator for the Protein C; or exogenous activated Protein C or exogenous Protein C together with an activator of Protein C; b) a suitable coagulation activator; c) an exogenous synthetic substrate for either Factor Xa or thrombin comprising a photometrically measurable leaving group; d) calcium ions; and e) said further metal(s) ions; in separate containers and/or in containers comprising mixtures of at least 0 two of said components in aqueous solution or in lyophilized form.

A further preferred embodiment of the present invention relates to a kit for use in the the above methods comprising the following components: a) an activator for the Protein C: or exogenous activated Protein C or exogenous Protein C together with an activator of Protein

C;

b) a suitable coagulation activator; c) an exogenous synthetic substrate for either Factor Xa or thrombin comprising a photometrically measurable leaving group; d) calcium ions; e) said further metal(s) ions; f) coagulation factors; and in separate containers and/or in containers comprising mixtures of at least two of said components in aqueous solution or in lyophilized form.

-22- A still further embodiment of the present invention comprises a reagentfor use in the above methods comprising said further metal(s) ions and at least one of the following components a) to eJ: a) an activator for the Protein C; or exogenous activated Protein C or exogenous Protein C together with an activator of Protein

C;

b) a suitable coagulation activator; c) an exogenous synthetic substrate for either FactorXa or thrombin comprising a photometrically measurable leaving group: d) calcium ions; and e) coagulation factors; in one container in aqueous solution or in lyophilized form.

According to a preferred embodiment, said reagent comprises at least two of said components a) to e) and said further metal(s) ions in one container in aqueous solution or in lyophilized form.

One preferred embodiment of said reagent comprises activated Protein C. with or without calcium ions and said further metal(s) ions. One further preferred embodiment of said reagent comprises coagulation factors andProtein C activators and said further metal(s) ions, if desirable in combination with phospholipid(s). One further embodiment comprises Factor IX/IXa, Factor X/Xa and/or calcium ions and said further metal(s) ions or said further metal(s) ions in combination with Factor V/Va, Protein C and prothrombin. Optionally Factor VIII/VIIIa and/or thrombin may be combined with said further metal(s) ions. In a further embodiment said further metal(s) ions are combined with a Protein C activator, such as Protac®C or thrombin/thrombomodulin. Said reagent embodiments are suitably comprised in a container in aqueous solution or in lyophilized form.

A wide range of concentrations of reactants can be used in the methods of the present invention. The following. Table 1 presents suitable and preferred ranges for the various components used in the method and contained in the kits and reagents according to the present invention.

23 1 Table 1 Parameter Final concentration in final reaction medium Blood sample 0.02 10 preferably 0. 1-5 (v/v) FIX/FIXa I x10-5 Ix 1-6 maul/ FX/FXa I x10-15-5x 10-7mo/L FV/ FVa 1 x 1O-12 10- 7 mo1/L. preferably 2 x100 x 10-8 mau/L- FVII/FVlla 1 x 10-15 2 x 10-8 mol/L FVIII/FVIIla 1 x 10-4 5 x 10-1 IU/mL Prothrombin I x 109- 5 x 10-7' mau/L Thrombin I x 10-15 1 x 108ma/L Ca 2 ions 0.5 20 mnmol/L, preferably 1 10 mmol/L Mg 2 ions 20 pLmol/L 10 xnmol/L, suitably 100 t~mol/L 2 mmnol/L and preferably 200 pmol/L 1 mmxrxol/L.

Mn 2 Zn 2

CU

2

NI

2 Sr 2 and/or Cu+ ions 1 junol/L 2mmolfL. suitably 5 400 g.mol/L and D preferably 10,- 80 ji.mol/L Protein C/APC 1 x 10-10 1 x 10- 7 mol/L, p referably 5 x 10 -10 1 x 10-8 mol/L ProtacOC 1 x 10- 3 1 U/mL, preferably 2 x 10-3 m 0:3 /rnL Protein S 10- 9 -5 x 10-7 mau/L Tissue factor 10- 8 -o5 g/L. preferably 5 x 10-8 10- 6 g/L Thrombmn/ thrombornodulin 10-11 10-8 mol/L Phospholipid 1 x 106- 3 x 10- 4 mol/L Fibrin polymnerization inhibitor Range dependent of substance used Chromogenic substrate 10-5 5 x 10-3 mol/L PH 6.5 9.5. preferably 7-8.5 Ionic strength 0-0.6, preferably 0.01-0.25 -24- 1 j Suitable embodiments include preparation in aqueous solution or D, lyophilization in a container of one or more components presented in the above Table 1 such as a protein with and without metal(s) ions, optionallyin nl 5 the presence of phospholipid to provide suitable reagents for use in the method according to the invention. Said embodiments may comprise e.g.

SProtein C or APC and said further metal(s) ions and with calcium ions and S with or without an active enzyme such as Factor IXa or Factor Xa. Other em- S bodiments may comprise metal(s) ions with any or a combination of Factor V/Va, Protein S. prothrombin, Factor X. Factor VIII/VIIIa, thrombin. Afurther embodiment may comprise a Protein C activator such as Protac®C or thrombin/thrombomodulin with metal(s) ions.

The Inethods of the present invention allow for convenient reaction times such as 1 -10 min. preferably 2-5 min, to provide for easy applicability to automated coagulation instruments.

The invention is also concerned with kits and reagents for use in the above in vitro methods for screening and diagnosing for Protein C and Pro- 3 tein S deficiency and for mutations in Factor V which affect the anticoagulant activity of APC. The invention is further concerned with a kit for an in vitro method for screening and diagnosing for defects in the Protein C pathway, caused by e.g. Protein C deficiency. Protein S deficiency and Factor V mutations. Said kits comprise a suitable selection of components listed in Table 1, prefereably present as reagents in one or more container(s) comprising said components in aqueous solution or in lyophilized form.

The invention is illustrated by the following examples which, however, in no way restrict the scope of the claims.

Example 1 Effect of manganese and magnesium ions on the determination of Protein C activity in a three-stage chromogenic thrombin generation assay using the Protein C activator Protac®C.

D ~Samples: Protein C deficient plasma (Biopool. -U~mt2., Sweden) with .and "A ~without addition of purified human Protein C (chrmongenix AB) to yield 0,: 0.1. 0.5 and 1.0 IU/mL of Protein

C.

Sample dilution: 1:41 in 25 rnrol/L Tris RCi p. do! aI 0.2% bovine serum albuimin.

D ~Protein -C activator: Pro tac®C was'used as a:3tc, k s-o1l,,on contain- O ing 10 U/mL. Final concentration during activati'jn of Pro~enC=01 D U/mL. Mg 2 and Mn 2 ions were added to yield final coucentrations during activation of Protein C of 0.4 and 0.04 rnroi/L, rnspc..ztive.

Reagent 1: Bovine Factor IXa (Enzyme Research, Sc. Uih Bend. Ill., USA), 180 pmol/L Bovine FX (Chromogenix AB). 0.3 U/niL Reagent 2: Phospholipids* (Chromogenix AB). 6C Rin ,1/L Gly-Pro-ArgPro, 0.36 mg/mL (polymerization inhibitor) Human Factor V. 0.2 TJ/mL CaC1 2 6 and 24 mrnol/L (final cone~. in assay =1.5 and 6 mmoi/L) 3 )A mixture of purified phospholipids containing 43% phospilatidyl cho line. 27% Phosphatidylserine and 30% sphlngomryelin.

Chromogenic thrombin substrate: S-2796 (Chromoge),ix 2 mmol/L Assa in a micropate: This assay is carried out as a three-stage method comprising, in the first stage, combining 50 jIL of the diluted plasma with 50 p.1 of the Protein

C

activator Pro tacOC and incubating this mixture for three minutes at 37*C, whereafter coagulation is activated by adding 50 pLLof Reagent 1 and 50 p.L of Reagent 2 and incubating the mixture for five minutes at 37"C, whereafter, in the third stage, the substrate hydrolysis is carried out by addlngsO p.L of the chroniogenic thrombin substrate S-2796 and incubati ng for four minutes at 37 0 C. The reaction is then terminated by lowering the pH 26 I through addition of 50jiL of 20% acetic acid. Thereafter the optical density (OD) of the samples in the microwells is recorded at 405 and 490 nrn and the differkence in optical density between 405 and 490 nxn, OD405-.490nm, is calculated:. This three-stage reaction is s'chemadtically s§hown as follows*.

Pro tein C' activation: Coagulation activation Plasma di lution 50 p4L Protein C activator 50 j*LL 3 min. 370C1 Reagent 1 5 0 ;L Reagent 2 5 0 IL min, 37 0

C

S-2796 4 min, 370C IlOAc. 20% 50 p.L Substrate hydrolysis 'Recording of O4540 Results: Protein

C,

0 Ca 2 6 minol/L Ca 2 l.5'mmol/L Mn 2 0.04 mmoi/L C2.1.5 nimol/L Mg 2 0.4 mmolIL 0.542 0.564 0.541 ILI/mnL 0.1 0.515 0.44 1 0.441 -0.5 0.503 0.231 0.230 0.467 0.076 0.069 The results demonstrate that by including manganese and magnesium ions in a reaction system containing calcium ions, a strong enhancemnent of the anticoagulant activity is obtained, manifested by the fact that increasing concentrations of Protein C in the samples result in a much de- -27- 1 creased absorbance, i.e. a much decreased thrombmn generation. in contrast, in the presence of calcium ions alone, there is a much lowe~r resolu..

tion. in absor bance, i. e. in thromnbin generation. at increasing Protein C con centrations. Thus, the addition of furthermentaI ions constitutes'an irn- .fl 5 proved method for determination of Protein C activity.

Example 2 Effect of different metal Ions on determination of Protemn C activity In [0 a three-stage thrombin generation assay using a four-fold lower concentration of Protein C activator.

Experimental conditions as in Example 1. except for the use of a3 final concentration of the Protein -C activator (Protac®C) of 0.043 U/mL.

Mg 2 +.Mn 2 Zn 2 and N, 2 tons were added to yield,final concentrations during activation of Protein C of 0.4 mmol/L (Mg 2 or 0.04 mmol/L. Zn 2 ions, Mn 2 ions and Cu 2 ions were also added to yield a final concentra-* tion of 0.08 znmol/L. Ca 2 was also used at final concentrations 'of mmol/L and 6.6 mmol/L in the absence of other metal ions.

Results: The results are shown in the table below with all primary data, which also includes a comparison between final concentrations of 0.04 and" 0.08 mnrol/L for Mn 2 and Zn 2 Protein C. IU/m.L 0 0.1, 0.5 C2,6 mmol/L 0.652 0.633 0.559 0.505 Ca 2 1.5 mrnol/L 0.640 0.585 0.504 0.438 Ca 2 1.5 mxnol/L Mvn 2 0.04 minol/L 0.725 0.689 0.503 0.237 C2,1.5 mmol/L M2,0.08 xnmol/L 0.627 0.469 0.145 0.056 C2,1.5 rnmol/L 28- 1 Mg 2 0.4 mmol/L 0.627 0.583 0.361 0.123 Ca2+. 1.5 mmol/L 0 Zn2+ 0.04 mmol/L 0.513 0.446 0.334 0.129 Ca 2 1.5 mmol/L Zn 2 0.08mmol/L 0.421 0.189 0.051 g Ca 2 1.5 mmol/L O Ni2+. 0.04 mmol/L 0.594 0.437 0.173 0.047 0 Ca2+, 1.5 mmol/L O Cu 2 0.08 mmol/L 0.487 0.425 0.348 0.099 0 The above results further graphically shown in Figure 2 demonstrate that many different metal ions provide an enhancement of the anticoagulant activity and also that a calcium concentration of 1.5 mmol/L in the absence of any other added further metal ions lacks the anticoagulation eni hancement property. Furthermore, the concentration of Protae®C is not critical since the use of a four-fold lower concentration of this component still results in apronounced anticoagulant activity in the presence of added metal ions.

Example 3 Effect of metal ions on determination of Protein C activity in a twostage thrombin generation assay.

These experimental details are as described in Example 1. with the following exceptions: the final concentration of the Protein C activator (Protac®C) was 0.043 U/mL during activation of Protein

C.

the chromogenic thrombin substrate used was S-2846 (Chromogenix AB), S the chromogenic substrate was included in Reagent 1, purified human Protein C was added to Protein C deficiency plasma to yield 0. 0.1 and 0.5 IU/mL, 29 metal ions tested: Mn 2 and Mg 2 Results, expressed as OD4O~~m 5 a) Mn 2 ions Protein C, IU/mnL Cl 00.1 ID C .6 rmnol/L 1.18 1.07 0.669 Ca 2 t. 1.5 znmol/L 0 Mn 2 0.04 mniol/L 1.36 1.17 0.258 b) Mg 2 ions Protein C, 1U/mrL 0 0.1 iC2 6 rnxol/L 1.24 1.05 0.554 Ca 2 t. 1.5 mmol/L Mg 2 0.4 rnmol/L .1.45 1.15 0.215 These results show that a significantly higher resolution for the different Protein C activities is obtained when Mn 2 and Mg 2 Ions are added to a final concentration of 0.04 mmol /L and 0.4 mmol/L, respectively, thus constituting an improved two-stage method for determination of Protein C activity.

Example 4 Effect of manganese ions on determination of Protein C activity in a two-stage thrombin generation assay using a phosphoipid emulsion from bovine brain.

Phospholipid source: Cephotest (Nycomed, Oslo, Norway) Experimental details as in Example 3. The final concentration of Cephotest was 3% 30 1 Results, expressed as OD405-490nm: c-i Protein C, IU/mL 0 0.1 Ca 2 6 mxnol/L 1.09 0.813 0.375 C2.1.5 mnrol/L Mn 2 0.04 mmol /L 1.366 0.996 0.163 cIN The results show that the same enhancing effect on the Protein C an 3 ticoagulant activity is obtained with a crude phospholipid extract from an animal tissue source. Hence, the source of phospholipid is not critical.

Example Effect of manganese and magnesium ions on determination of free Protein S activity in a chrornogenic Factor Xa generation assay.

Sample: Protein S deficient plasma (Biopool) with or without addition of purified human Protein S to yield 25% and 100% Protein S." Sample dilution: 1:61 in 50 mmolfL Tris buffer pH 8.2.0.15 mol/L NaCi.

0.2% BSA Factor reagent. (concentration in assay before substrate addition): Bovine FIXa (4 mtJ/mL) Bovine FX (0.3 U/mL) Human FVIII (0.02 U/mL) Human FV (0.02 U/mL) Human prothrombin (0.01 U/mL) Phospholipids (21 j.tmol/L) Mg 2 (0.4 xnmol/L) or Mn 2 (0.04 mmol/L) or no addition Medium: 10 minol/L MES pH 6.0. 0.15 mol!L NaCJ, 0.2% BSA- Start reagent Human APC (0.35 [Lg/mL) CaCl 2 (1.5 mnlol/L) -31 C 1 Chromoenic Factor Xa substrate: S-2765 (ChromogenixAB), 1.8 mmol/L.

For carrying out the assay 50 iL of the diluted plasma sample was f 5 mixed with 50 L of the above Factor reagent, whereafter the mixture was incubated for three minutes at 37°C. Thereafter, 50 pL of the Start reagent S comprising human APC and calcium chloride was added and the mixture O incubated for four minutes at 37°C. Following that, 50 pL of the chromogen- Sic substrate S-2765 was added to and the reaction mixture incubated for 0 two minutes at 37*C, whereafter 50 uL acetic acid was addedto terminate the reaction. The absorbance of the sample was then determined according to Example 1 and expressed as OD 4 0 5 4 9 0 nm- Assay: Factor reagent 50 j.L SSample dilution 50 pL Incubation 3 min, 37°C APC/CaCI 2 50 pL 4 min, 37C S-2765. 1.8 mmol/L 50 pL 2 min. 37C HOAc, 20% 50 IL Results: All primary data are listed in the table below and also illustrated in Figure 3.

Free Protein S. 0 25 100 Ca 2 1.5 mmol/L 0.857 0.642 0.364 Ca 2 1.5 mmol/L Mn 2 0.04 mmol/L 1.53 1.34 0.745 Ca 2 1.5 mmol/L Mg 2 0.4 mmol/L 1.053 0.851 0.378 Figure 3 shows that the addition of Mg 2 or Mn 2 ions results in a greater resolution, a greater slope of the curve) as well as in amorelinear dose response when compared to the use of Ca 2 alone, thus constitut- -32- 1 ing an improved method for determination of Protein S activity.

Example 6 Effect of strontium ions on the determination of free Protein S activig ty in a chronogenic Factor Xa generation assay.

O The experimental details are as disclosed in Example 5 but with the 0Factor reagent stored for one hour before assay.

Results: Absorbances expressed as OD 4 0 5 4 9 0 n m Free Protein S, 0 25 100 Ca 2 1.5. mmol/L 0.673 0.488 0.258 Ca 2 1.5 mmol/L Sr 2 0.4 mmol/L 0.848 0.611 0.276 The results show that a higher resolution for various Protein S activity levels is obtained on addition of Sr 2 ions supporting the enhancing effect of Sr 2 on the Protein C anticoagulant pathway activity.

Example 7 Effect of metal ions on the detection of Protein S deficiency in a global chromogenic method for the Protein C anticoagulant pathway, using tissue factor as activator of coagulation and monitoring thrombin generation.

:Samle: Normal human plasma pool and Protein S deficient plasma (Biopool. UmeA. Sweden) Sample dilution: 1:21 in 25 mmol/L Tris-HCI pH 7.6, 20mmol/L NaCI.

0.2% bovine serum albumin.

Protein C activator:Protein C activator (Protac®C) from Coamatic Protein C. was reconstituted in 7.2 mL according to the kit package insert and then -33- 1 diluted in 25 mmol/L Tris-HCI pH 7.6, 20 mmol/L NaCI, 0.2% bovine serum albumin to yield a concentration during Protein C activation of 0.02 U/mL.

Human prothrombin (Chromogenix AB) was added to yield a final concentration after addition of tissue factor of 1.5 ig/mL.

The analysis was-performed with or without Mg 2 ions added to the Protac®C solution.

Reagent: Tissue factor: Thromborel (Behringwerke, Marburg, Germany). Reconstituted in 2 mL water according to the manufacturer, thereafter diluted in 25 mmol/L Tris-HCI pH 7.6, 20 mmol/L NaCI, 0.2% bovine serum albumin to yield a final concentration during activation of coagulation of 0.033% Phospholipids (43% phosphatidylcholine, 27% phosphatldylserine and sphingomyelin): Final concentration during activation of coagulation of 16.7 p.mol/L.

CaCi 2 6.6 mmol/L final concentration during activation of coagulation.

3 Chromogenic thrombin substrate: S-2796 (ChromogenixAB). 1.8 mmol/L For carrying out the assay 50 pL of the diluted plasma sample was mixed with 50 iL of the Protein C activator. whereafter the mixture was incubated for two minutes at 37°C. Thereafter. 50 pL of the reagent comprising the tissue factor was added and the mixture incubated for two minutes at 37°C. Following that. 50 IL of the chromogenic substrate S-2796 was added and the reaction mixture incubated for four minutes at 37*C, whereafter 50 L acetic acid solution was added to terminate the reaction. The absorbance of the sample was then determined according to Example 1 and expressed as OD 4 0 5- 4 9 0 nm.

Microplate Assay: Sample dilution 50 IL Protac C activator 50 iL 2 min, 37"C -34- I Reagent 50 gL S2 min, 37°C

S

S

-2796 50 pL 4 min, 37"C S 5 HOAc,20.% 50 p Results: Normal plasma Protein S def. plasma ID Ca 2 6.6 mmol/L 0.26 0.53 SCa 2 6.6 mmol/L 0 Mg 2 0.4 mmol/L 0.29 0.75 The results show that the addition of magnesium ions to calcium ions brings about a higher resolution at different Protein S activity levels thus improving detection of Protein S deficiency.

Example 8 Effect of metal ions on resolution between different levels of free Protein S and for detection of FV:Q506 in a global method for the Protein C anticoagulant pathway using Factor Xa as activator of coagulation and monitoring thrombin generation.

Experimental details as in Example 7, but with bovine Factor Xa (Chromogenix AB) used instead of tissue factor as activator of coagulation.

Concentration of Factor Xa 1.4 ng/mL during activation. Furthermore, a stock solution ofProtac®C, containing 10 U/mL, was used. which was then diluted in 25 mmol/L Tris-HCI pH 8.4, 0.2% bovine serum albumin to yield a concentration during protein C activation of 0.02 U/mL.

SaEmles: 100% protein S normal human plasma pool 0% protein S protein S deficient plasma 25% protein S protein S deficient plasma pg/mL purified human protein

S.

Furthermore, a sample from an individual with heterozygosity for the factor V mutation (FV:R506Q) was analysed.

Results: rsnsalpiaydt x See Figure 4. The table belowprsnsalrirydtex pressed as OD 4 0 5 -490nrn.

Ca 2 +C 2 Saple. OLY Ca 2 0.04 MM Mn 2 0.4mMM 2 100% Protein 9 0.222 0.309 0.41 Protein S 0.411 0.4850.6 0% Protein S 0.650 0..7 6.14 FV:R506Q 0.402 0.91.17 The results show that a highler resolu ti on i obtained for Protein'S deficiency In the 0 100% range as well as a high discrimination for the FV: 506 muttio whn M 2 +or Mn Ions are included in the reaction mixture, thus proving the-beneficial use Iof added metal ions In a global chromogenic method.

Example 9 Comparison between a global chromogenic method according to the invention,. using Factor Xa. as coagulation activator, with a global clotting method according to theprior art usingAPTT as cogulation activator. :e. garding resoluition between different levels of, respectively. Protein C anMd Protein S activity and regarding analysis of plasma from pregnant women.

Samples: Human normal plasma pool (NPL), three plasmas from healthy individuals (N 1 four plasmas from pregnant women (P1I -P4) and plasmas with 0% and 50% deficiency of Protein C and Protein S, respectively, the levels being prepared by adding purified human Protein C (Chromogenix AB) or Protein S (Chromogenix AB) to plasmas deficient in either Protein C or S (both from Biopool

AB).

Global chromoj;enic assay: Experimental details and assay, see Examples 7 and 8. A stock solution'of ProtacOC. containing 10 U/imL, was used which 36 I was then diluted to yield a final concentration du'ring activation Of Protein C =0.02 Lt/mL. Metal ion used Mn 2 which'was added 6o the PI-otac@C solution to yield 0.04 mrnol/L in the Pro teinh' acilvati on step. The analysis was performed in a microplate and the OD405..4'9nm was determined as described in Example 1. A high OD 4 os..

4 6*ccrespands to pronounced thromnbi: iformation and thus an impaired Pr-oter anticoagulant pathway activity.

Global clotting assay using APTraetATragent from. Coats®PC Resistance was used at a final phospholipid corcentration of 33 4mol/L during coagulation activation. For activation: of Protein C, the same ProtacOC stock solution and dilution medium was used as for the chrornogenic assay. Final concentration during activation of Protein C 0.083 U/mL, The. analysis was performed. in a ST-4'coa~ulation analyzer (Diagnostica Stago).

Assay Plasma sample 50 IL Protac®C or buffer 50 IL APTT reagent 50 L Activation for 3 min, 37*C Ca 2 4. 25 mmol/L 5 0 IL The clotting time in seconds was determided in the presexiqe and absence of Pro tac®C and a clot time. rati'O (CTR)was calculated as CTR CT+/ CT-. A low CTR corresponds to a pronounced thrombin formation also In the presence of Pro tac®C and hence an lmpaired'Protein C anticoagulant pathway activity.

Results: Sample Chromogenic

APTT

OD40-490CTR NPL 0.202 3.77 NI 0.183 5.17 37 N.2 N3 P1 P2 'P3 P4 Pr S 0% Pr S Pr C 0%Pr C 0.182 0.186 0.221 0.298 0.239 0.259 0.578 0.802 0.456 1.084 3.50 4.85 3.15 2.21 2.60.

2.66 3.48 1.80 3.86 1.18 The results demonstrate that a) for samples with 50% deficiency of .either Protein C or Protein S a higher resolution versus the normal samples and b) for samples fromn pregnant women a smaller deviation from normal samples is obtained with the chromogenic assay, thus supporting that a higher sensitivity and specifictywil be obtained with a global chromogenic assay accord[ing to the invention as compared to a global clotting method according to the prior art.

0 Example Effect of a Mixure of...Mg 2 and Mn 2 4- In a phospholipid reagent or In an APC reagent on discrimination for the FV:QsoG mutation in a c hromx. o- genic thrombin gencration assay Using Factor Xa as activator.

(R506 an Plam a wgith ornal factor V (R506R) and with. hetero- S 6 Q n d h m o z y osit Q 0 6 Q j fo r F V Q5 o6 m u ta tio n Sample diluton 1:41 in 0.05 Mol/L Wepes pHI 7.7, 0.15 mol/L NaCI.

Rage nt A: Human prothrombin. 19 p1g/mL Phospholipids (43% phosphatidylcholine, 27% phospliatidyl.

serine and 30% sphingomyeljn), 50 i unol/L 38 IReaent B: Bovine Factor Xa, 0.2 nmol/L APC, 6 [Lg/mL Cadl 2 25 mmzol/L Chromooenic thrombin substrat S-2 796 (Chromogenix ADL) 1.8 mnrol/L Mixture of metal ions: Mg 2 0.4 mmol/L, an .d Mn.

2 40.04 rnn-:61/L'included in either Reagent A or Reagent B.

For carrying out the assay 50 4i of Reagent Awas mixed with 504 ~of Reagent B, whereafter the mixture was ndubated for three minutes at 37*C.

Thereafter. 50 p.L of the plasma dilution was added and incubated for two minutes at 37*C. Following that, 50 IAL of the chromogenic substrate

S-

2796 was added and inetic reading was performed. The change in aD 4 0 5 490 per minute was determined and expressed as A0D405..

4 9 0 /min.

Assay Reagent A 50 &LL Reagent B 50 L Incubate at 3 7 Cfor 3 min Plasma dilution 50 jL 2 min. 37*C S-2796 50 p.L Kinetic reading Results: Mg 2 and Mn 2 Mg 2 and Mn 2 in Reagent A in Reagent B FV:R506R 0.143 0.193 FV:R506Q 0.646 0.616 FV:Q506Q 1.116 0.942 The results show that a mixture of metal ions such as Mg 2 and Mn 2 maybe added in a phosphoipid containing reagent (ReagentA) orin a reagent containing active enzymes such as APC and Factor Xa (Reagent B)and provide a high discrimination for the FV:Q506 mutation. Hence the -39- 1 addition of further metal(s) ions is not restricted to any unique reagent.

Example 11 Substitution of chloride anions with nitrate and sulfate anions In a study on the effect of magnesium and manganese in determination of Protein C activity in a three-stage thrombin generation assay.

Experimental details as in Example 1.

Magnesium nitrate (Mg(NO 3 2 1 and manganese sulfate (MnSO 4 were used instead of the corresponding chloride salts at final concentrations in the assay of 0.4 and 0.04 mmol/L respectively in accordance with the conditions in Example 1. Absorbance readings are expressed as OD405-490nm- Results: Protein C, IU/mL 0 0.1 0.5 Ca 2 1.5 mmol/L Mn 2 0.04 mmol/L 0.563 0.541 0.278 -0.079 Ca2+. 1.5 mmol/L Mg 2 0.4 mmol/L 0.603 0.554 0.448 0.154 The results show that a similar high resolution is obtained as when using chloride as an anion (cf. Example Thus, the choice of the anion is not restricted to chloride ions.

Example 12 Effect of metal ions on the detection of Protein C deficiency, Protein S deficiency and FV:9506 in a global chromogenic method for the Protein

C

anticoagulant pathway, using recombinant tissue factor as activator of coagulation and monitoring thrombin generation, Experimental details as in Example 7, but using recombinant tissue factor (PT-Fibrinogen Recombinant. Instrumentation Laboratory, Milano, Italy) instead of Thromborel as activator of coagulation. PT-Fibrinogen 1 Recombinant was reconstituted with 8 mL of water according to the manufacturer's instructions, thereafter diluted in 25 mmol/L Tris-HCI pH 7.6, mmol/L NaCl, 0.2% bovine serum albumin to yield a final concentration during activation of coagulation of 0.25% Samples: Normal human plasma. Protein C deficient plasma and Protein

S

deficient plasma (Instrumentation Laboratory. Milano, Italy). Plasmas with activity of Protein C and Protein S. respectively, were prepared by mixing normal human plasma with the Protein C or Protein S deficient plasmas respectively. Furthermore, a sample from an individual with heterozygosityfor the factor V mutation (FV:R506Q) and from an individual with homozygosity for the same mutation (FV:9506Q) were analyzed.

The analysis was performed with or without Mg 2 ions added to the Protein C activator solution.

Results: See Figure 5. The table below presents all primary data expressed as OD405-490nm- 6.6 mM Ca 2 Sample 6.6 mM Ca 2 t 0.4 mM Ma2 Normal Plasma 0.881 0.364 25% Protein C 1.225 1.047 0% Protein C 1.418 1.388 Protein S 1.325. 0.837 0% Protein S 1.456 1.421 FV:R506Q 1.140 0.686 FV:Q5069 1.392 1.398 The results show that the presence of magnesium ions during the Protein C activation and during the ensuing thrombin generation provides an enhancement of the anticoagulant activity (see results for normal plas- -41 1 ma). Furthermore, the enhanced anticoagulant activity results in a higher resolution at different Protein C and Protein S activity levels respectively, as well as higher discrimination for the FV:Q506 mutation.

Example 13 Effect of manganese ions on the discrimination at different Protein S activity levels in a global chromogenic method for the Protein C anticoagulant pathway, using tissue factor as activator of coagulation and monitoring thrombin generation.

Experimental details as in Example 7, using Protac® C as Protein C activator and Thromborel as activator of coagulation.

Samples: Normal human plasma (Instrumentation Laboratory, Milano, Italy) as 100% free Protein S sample: Protein S deficient plasma (Instrumentation Laboratory. Milano, Italy) as 0% free Protein S sample; plasma samples were prepared by mixing normal human plasma and Protein S deficient plasma to yield 20%, 40%, 60% and 80% free Protein S activity respectively.

The analysis was performed with or without Mn2+, ions, respectively, added to the Protein C activator solution.

Results: All primary data expressed as OD405-490nm are listed in the table below and also illustrated in Figure 6.

6.6mM Ca 2 Sample 6.6mM Ca_ 2 +0.04mM Mn 2 0% Protein S 0.458 1.371 Protein S 0.407 0.756 Protein S 0.388 0.570 Protein S 0.367 0.493 Protein S 0.348 0.439 42- 1 100% Protein S 0.325 0.379 Figure 6 shows that the addition of Mn2+ions dramatically increases the resolution when compared to the use of Ca 2 alone, thus constituting an improved detection of Protein S deficiency in a global chromogenic method for detection of deficiency states of components in the Protein C anticoagulant pathway.

Example 14 Effect of magnesium and manganese ions on the discrimination at different Protein C activity levels in a global chromogenic method for the Protein C anticoagulant pathway, using recombinant tissue factor as activator of coagulation, a recombinant Protein C activator and monitoring thrombin generation.

Experimental details as in Example 7, but using recombinant Protein C activator as Protein C activator and recombinant tissue factor (PT-Flbrinogen Recombinant, Instrumentation Laboratory) as activator of coagulation. Recombinant Protein C activator was used as a stock solution containing 26 U/mL. The recombinant Protein C activator was then diluted in 25 mmol/L Tris-HCI pH 7.6, 20 mmol/L NaCI, 0.2% bovine serum albumin to yield a final concentration during activation of Protein C of 0.025 U/mL. PT-Fibrinogen Recombinant was prepared as in Example 12 to yield a concentration during activation of coagulation of 0.17% Samples: Normal human plasma (Ins trumenation Laboratory, Milano, Italy) as 100% Protein C sample; Protein C deficient plasma (Instrumentation Laboratory. Milano, Italy) as 0% Protein C sample; plasma samples were prepared by mixing normal human plasma and Protein C deficient plasma to yield 20%. 40%, 60% and 80% Protein C activity respectively.

The analysis was performed with or without Mg 2 or Mn 2 ions, respectively, added to the recombinant Protein C activator solution.

-43- 1 Results: All primary data expressed as OD40549nm are listed in the table below and also illustrated in Figure 7.

6.6mM Ca 2 6.6mM Ca 2 Sample 6.6mM Ca2+ +0.4mM M2± +0.4mMMn± 0% Protein C 1.442 1.483 1.451 Protein C 1.253 1.219 1.097 40% Protein C 1.010 0.900 0.636 Protein C 0.783 0.675 0.438 Protein C 0.787 0.569 0.356 100% Protein C 0.672 0.456 0.280 Figure 7 shows that the addition of Mg 2 or Mn 2 ions results in a higher resolution for the different Protein C activities when compared to the use of Ca 2 alone, thus resulting in an improved detection of Protein C deficiency in a global chromogenic method for detection of deficiency states of components in the Protein C anticoagulant pathway. The results further iilustrate the applicability of recombinant sources of tissue factor and Protein C activator.

Example Effect of the combination of Mg 2 and Mn 2 ions on the detection of Protein C deficiency, Protein S deficiency and FV:Q506 in a global chromogenic method for the Protein C anticoagulant pathway, using tissue factor as activator of coagulation and monitoring thrombin generation.

Expermimental details as in Example 7, using Protac C as Protein

C

activator and Thromborel as activator of coagulation.

Samples: Normal human plasma. Protein C deficient plasma and Protein

S

deficient plasma (Instrumentation Laboratory. Milano, Italy). Further- -44- 1 more, a sample from an individual with heterozygosity for the factor V mui tation(FV:R506Q) and from an individual with homozygosity for the same

O

mutation (FV:Q506Q) were analyzed (r 5 The analysis was performed with or without the presence of the N combination of Mg 2 and Mn 2 ions added to the Protein C activator O solution.

O

0 Results: See Figure 8. The table below presents all primary data expressed )as AAbnormal Normal DO 4 0 5 .490 abnormal plasma DO 4 0 5 4 9 0 normal plasma).

6.6 mM Ca2+ 0.4 mM Mg2+ Sample 6.6 mM Ca2+ 0.04 mM Mn24 0% Protein C 0.425 0.801 0% Protein S 0.372 0.742 FV:R506Q 0.060 0.413 FV:9506Q 0.530 0.664 The results show that the addition of the combination of magnesium and manganese ions to calcium ions provide a higher resolution for both Protein C and Protein S deficiencies, as well as a higher discrimination for the FV:Q506 mutation, thus proving the beneficial use of adding a combination of metal ions in a global chromogenic method.

P\OPERUg,0)039.9" diMirio-I.d.)IMj7M3 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference toany prior art in this specification is not, and should not be taken as, an acknowledgment or any form or suggestion that that prior art forms part of the common general knowledge in Australia.

-It would be appreciated by a person skilled in the art numerous variations and/or modifications may be made to the invention as shown the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (38)

1. A kit for determining the activity of one or more components of a Protein C anticoagulant pathway, the kit comprising the following components: a procoagulant reagent; calcium ions; and at least one metal ion that increases anticoagulant activity of the Protein C anticoagulant pathway, the metal ion selected from the group consisting of Mg 2 Mn 2 Zn 2 Ni" 2 Sr 2 Cu and Cu wherein the components are in separate containers and/or in containers comprising mixtures of at least two of the components.

2. The kit of claim 1 further comprising an exogenous substrate for an enzyme influenced by Protein C anticoagulant activity.

3. The kit of claim 2 wherein the exogenous substrate for an enzyme influenced by Protein C anticoagulant activity is synthetic.

4. The kit according to claim 1, wherein the metal ion comprises Mg" 2 The kit according to claim 1, wherein the metal ion comprises at least one of Mn 2 Zn 2 Ni 2 Sr 2 Cu 2 and Cu+.

6. The kit according to claim 2, wherein the exogenous substrate comprises a substrate for a component of the coagulation cascade selected from the group consisting of Factor Xa and thrombin.

7. The kit according to claim 6, wherein the substrate is selected from the group consisting of Benzoyl-Ile-Glu-Gly-Arg-pNA, N-a-Z-D-Arg-Gly-Arg-pNA, CH3S02 -D-Leu-Gly-Arg-pNA, and MeO-CO-D-CHG-Gly-Arg-pNA.

8. The kit according to claim 6, wherein the substrate is selected from the group consisting of H-D-Phe-Pip-Arg-pNA, pyroGlu-Pro-Arg-pNA, H-D-Ala Pro-Arg-pNA, Z-D-Arg-Sarc-Arg- pNA, AcOH*H-D-CHG-But-Arg-pNA, and H-D-HHT-Ala-Arg-pNA.

9. The kit according to claim 2, wherein the exogenous substrate comprises a photometrically measurable leaving group. The kit according to claim 9, wherein the photometrically measurable leaving group is selected from the group consisting of a chromophore, a fluorophore, and a luminophore.

11. The kit according to claim 10, wherein the chromophore comprises a p-nitroaniline group (pNA).

12. The kit according to claim 10, wherein the fluorophore comprises a naphthylamine or coumarine derivative group.

13. The kit according to claim 10, wherein the luminophore comprises an isoluminolamide group.

14. The kit according to claim 1, wherein the procoagulant reagent comprises one or both of a phospholipid and a contact activator. The kit according to claim 1, wherein the procoagulant reagent comprises at least one phospholipid and at least one intrinsic pathway factor selected from the group consisting of Factor IXa, Factor XIIa, and Factor XIa.

16. The kit according to claim 1, wherein the procoagulant reagent comprises at least one phospholipid, at least one contact activator, and at least one intrinsic pathway factor selected from the group consisting of Factor IXa, Factor XIIa, and Factor XIa.

17. The kit according to claim 14, wherein the phospholipid is selected from the group consisting of a synthetic phospholipid, a purified phospholipid, and a crude extract of a phospholipid derived from a biological source.

18. The kit according to claim 14, wherein the at least one contact activator is selected from the group consisting of ellagic acid, collagen, a collagen-related substance, and silica.

19. The kit according to claim 18, wherein the silica is selected from the group consisting of micronized silica, colloidal silica, and kaolin. The kit according to claim 1, wherein the procoagulant reagent comprises at least one material selected from the group consisting of native human tissue factor, recombinant human tissue factor, native non-human tissue factor, recombinant non-human tissue factor, native human Factor VII/Factor VIIa, recombinant human Factor VII/Factor VIIa, native non-human Factor VII/Factor VIIa, and recombinant non-human Factor VII/ Factor VIIa.

21. The kit according to claim 14, wherein the phospholipid is selected from the group consisting ofphosphatidylcholine, phosphatidylserine, and sphingomyelin.

22. The kit according to claim 1, wherein the procoagulant reagent comprises a material selected from the group consisting of exogenous Factor Xa, exogenous Factor X and an exogenous activator of Factor X, and an exogenous activator for endogenous Factor X.

23. The kit according to claim 22, wherein the exogenous activator for Factor X comprises snake venom enzyme.

24. The kit according to claim 23, wherein the snake venom enzyme comprises Russelli Viperii snake venom enzyme. The kit according to claim 1, the kit further comprising at least one component selected from the group consisting of Protein C, activated Protein C, Protein S, Factor V, and Factor Va.

26. The kit according to claim 1, the kit further comprising a fibrin polymerization inhibitor.

27. The kit according to claim 26, wherein the fibrin polymerization inhibitor comprises Gly- Pro-Arg-Pro.

28. The kit according to claim 1, wherein the procoagulant reagent comprises at least one material selected from the group consisting of Factor VIII/Factor Villa, Factor X, and prothrombin.

29. The kit according to claim 1, the kit further comprising exogenous activated Protein C. The kit according to claim 1, the kit further comprising an activator of Protein C.

31. The kit according to claim 1, the kit further comprising an exogenous Protein C and an activator of Protein C.

32. The kit according to claim 30, wherein the activator of Protein C comprises at least one of Protein C activating snake venom enzyme and thrombin.

33. The kit according to claim 30, wherein the activator of Protein C comprises thrombomodulin and thrombin.

34. The kit according to claim 30, wherein the activator of Protein C is a recombinant protein. The kit according to claim 32, wherein the snake venom enzyme is derived from the Agkistrodon family.

36. The kit according to claim 32 wherein the snake venom enzyme is derived from Agkistrodon contortrix contortrix.

37. The kit according to claim 32, wherein the snake venom enzyme comprises crude snake venom enzyme.

38. The kit according to claim 32, wherein the snake venom enzyme comprises purified snake venom enzyme.

39. The kit according to claim 1, wherein the procoagulant reagent comprises Factor VIla and at least one phospholipid. (The kit according to claim 1, wherein the procoagulant reagent comprises at least one material selected from the group consisting ofprothrombin, Factor V/Va, Factor IX, and Factor X.

41. The kit according to claim 1, the kit further comprising a plasma deficient in at least one component selected from the group consisting of Protein C, Protein S, and Factor V.

42. The kit according to claim 1, the kit further comprising a plasma deficient in all components of the Protein C anticoagulant pathway.

43. The kit according to claim 1, the kit further comprising a plasma deficient in the Protein C anticoagulant pathway component to be measured.

44. The kit according to claim 16, wherein the phospholipid is selected from the group consisting of a synthetic phospholipid, a purified phospholipid, and a crude extract of a phospholipid derived from a biological source. The kit according to claim 17, wherein the phospholipid is selected from the group consisting of a synthetic phospholipid, a purified phospholipid, and a crude extract of a phospholipid derived from a biological source.

46. The kit according to claim 16, wherein the phospholipid is selected from the group consisting of phosphatidylcholine, phosphatidylserine, and sphingomyelin.

47. The kit according to claim 17, wherein the phospholipid is selected from the group consisting of phosphatidylcholine, phosphatidylserine, and sphingomyelin. DATED this 2 0 t h day of January 2006 Instrumentation Laboratory S.p.A. By DAVIES COLLISON CAVE Patent Attorneys for the Applicant