Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/8483—Investigating reagent band
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration

Definitions

• the present invention falls within the field of analysis of sample liquids using analyte-specific, disposable test elements.
• sensor measuring devices in which the blood glucose is determined on the basis of an electrochemical measurement
• optical systems in which an analyte-dependent color change on the test element serves to determine the analyte concentration
• test elements often represents a method for quickly determining the concentration of analytes in samples.
• test elements that are evaluated photometrically or by reflection photometry are of great importance.
• Common home monitoring analysis systems for determining the blood glucose content which are operated by the patient himself, contain test elements on which an analysis area is arranged which is brought into contact with the patient's blood.
• the test element is inserted into the device by the user.
• a suitable optical measuring system detects an optical change depending on the analyte concentration by means of the light reflected or transmitted by the test element, so that the concentration of the blood sugar can be determined.
• Such a system is described, for example, in document EP B 0 618 443.
• such devices are commercially available, for. B. available under the names Accutrend ® , Accu Check ® , Glucotrend ® and Glucometer®.
• test elements The structure of such test elements is shown for example in document US 6,036,919.
• Disruptive influences on the light intensity are such. B. caused by non-constant measuring conditions and by sample components in the analysis systems, which have an effect on the amount of light registered by a detector. Such analyte-independent changes in light intensity lead to falsified measurement results, so that, for. B. the glucose concentration is incorrectly determined.
• Detector is detected.
• fluctuations in the measurement conditions are caused by a non-constant performance of optical components, for example the lighting unit or the detector due to aging effects or contamination.
• test element contains light-conducting elements and thus forms part of the lighting unit.
• the light is coupled into the light-guiding elements of the test element, passed through and the transmitted or reflected light is coupled out again.
• Variances z. B. in the production of the test elements different connections of the test elements to the device optics or contamination, to name just a few factors, significantly influence the measurement results.
• the object of the invention is to determine non-constant instrumental measuring conditions of an analysis system which determines the analyte concentration on the basis of absorption measurements and to take this into account when correcting the measured value.
• the invention enables error correction due to non-constant measuring conditions within the analysis system.
• a preferred embodiment of the invention enables changes in sample light intensity to be detected in addition to the fluctuations in apparatus measuring conditions.
• the invention consequently allows a more precise calculation of analyte concentrations due to light absorption by the analyte, whereby a change in analyte-independent measurement conditions is taken into account.
• the analysis system includes a test element that has an absorption of light in a first wavelength range that is known and not equal to zero before sample application, an illumination unit that emits at least two different wavelength ranges and irradiates the test element, a detector unit that is positioned in this way, that transmitted or reflected light of the test element is registered and an evaluation unit with which a correction value is determined from an analyte-independent absorption of the test element in the first wavelength range and with which a measured value is determined in a second wavelength range from an analyte-dependent absorption of the test element.
• the concentration of the analyte is determined by means of the evaluation unit with a correction of the measured value taking into account the correction value.
• Lighting units in the sense of the invention are both those with an essentially continuous emission spectrum, such as. B. incandescent lamps, as well as those that have a so-called band spectrum, such as. B. LEDs.
• Light emitting diodes are particularly well suited for use in a portable analysis system because they have a relatively high degree of efficiency, which is important for battery-operated devices.
• LEDs are available for a number of wavelength ranges in the visible as well as in the infrared range. In principle, the light sources known in the prior art for diagnostic detection systems are suitable. Wavelength ranges that can be used in the context of the invention include UV and IR in addition to the visual range.
• Test elements in the sense of the invention are used for sample application, so that an analyte in the sample can be determined by the analysis system, the test element being designed in such a way that it has an absorption in a first wavelength range that is known and not equal to zero.
• test elements are designed in the form of strips in the sense of the invention.
• An absorbent carrier material is preferably applied to a holder which is used for handling.
• the test field there is, for example, a reagent layer that reacts with the analyte. The sample brought into contact with the detection zone leads to a detectable change in the test field in the test element.
• the analyte reacts with the reagent layer, which consists, for example, of a heteropolyacid and which is reduced by the analyte to the dye heteropoly blue.
• the formation of the dye takes place depending on the analyte concentration and is considered a change in the Test field detected in the visible range of the spectrum.
• the analyte is an electron-rich aromatic amine or is reacted with a substance to this.
• a substance can be a nitrosoaniline derivative which, in a preferred embodiment, has a previously known absorption in the first wavelength range.
• test element is subject, among other things, to certain manufacturing tolerances, so that measurement errors are thereby caused.
• test elements can include a light-conducting layer, in which total reflection preferably takes place.
• the light is coupled in through an input surface, which is preferably formed by a cut surface on the front face of the light guide layer.
• the refractive index of the light guide layer in the area of the detection zone can be changed so that total reflection no longer takes place. It is also possible to effect the coupling out of the light by means of a suitable light guide within the light guide layer. Possible embodiments of light-guiding test elements are shown in patent application WO 01/48461.
• the fluctuations in the measurement conditions caused by light-conducting test elements are detected by the analysis system according to the invention, so that a correction according to the invention is obtained when light-conducting test elements are used proves to be particularly cheap.
• detectors in particular semiconductor detectors
• Detectors that have their maximum sensitivity in the range of the reflected or transmitted radiation can advantageously be used.
• filters can also be used which selectively let the measuring radiation pass through in order to make the detection more stable against the effects of stray light.
• filters are particularly necessary when using lighting units with a continuous emission spectrum.
• the filters can be requested both from the lighting unit and from the detector in order to achieve a selection of desired wavelengths.
• the evaluation unit of the analysis system contains a module for error correction, which can be implemented, for example, with an operational amplifier.
• the evaluation unit registers the counts generated depending on the light intensity in the detector as a measure of a relative light intensity. By referencing the registered counts to a reference, e.g. B. the white value, whose registered counts are set equal to 100% of the light intensity, the evaluation unit calculates an absolute light intensity and the correction of this light intensity as described.
• the concentration can be determined on the basis of the light intensity.
• the use of calibration curves for determining the concentration is e.g. B. described in document EP 0 247439.
• the analysis system preferably contains an evaluation unit which additionally determines the light intensity detected by the detector in the second or in a third wavelength range, with essentially no absorption by the test element taking place in this wavelength range.
• the absorption values in a third wavelength range or in the second wavelength range, in which there is essentially no absorption in the wavelength range, are referred to as white values. If this white value is measured in a preferred manner in the second, same wavelength range as the analyte, the measurement is carried out on the test element before the sample is added. Consequently, no further optics for a wavelength range have to be provided for the determination of the white value.
• the evaluation unit calculates the measured value taking into account the white value, so that in addition to the detection of the correction value, an additional error correction takes place.
• the correction value of the analysis system which is measured in the first length range, can be e.g. B. can be determined on the basis of a dry test element which in the first wavelength range advantageously absorbs more than 50%, better more than 80%, particularly completely (approximately 100%) the light. Complete absorption of the dry test element proves to be advantageous, since error minimization therefore takes place for further calculation steps.
• the evaluation unit can thus detect or calculate the amount of light in this wavelength range, which is registered by the detector despite 100% light absorption of the test element. This measured value is referred to as the black value, since the idealized
• Behavior of the measuring apparatus no light would be detected. This means that the amount of light is registered in real behavior, which is not absorbed a priori by the test element and whose change z. B. is influenced by contamination of the test element, ambient light, quality differences in test elements, etc.
• the known absorption in the first length range is by an absorber present in the test element, such as. B. tartrazine, which does not interact with the sample, so that, for. B. Even after sample application, a known absorption is guaranteed.
• the test elements used advantageously have a light-conducting element and are coupled to a lighting unit, so that they represent part of the lighting unit.
• the correction value can also be measured on a wet test element after sample application. Under these conditions, the amount of light is recorded, which is registered by the detector in the case of previously known absorption of the test element and additionally sample-dependent absorption in the first wavelength range. A correction of the measured value by this correction value consequently takes into account the analyte-independent influence of the sample in the first wavelength range (e.g. sample's own color, change in the refractive index due to wetting) in addition to the change in apparatus measurement conditions.
• the analyte-independent influence of the sample in the first wavelength range e.g. sample's own color, change in the refractive index due to wetting
• the evaluation unit registers at least two correction values, the absorption of the dry test element before sample addition and the absorption of the wet test element after sample addition being recorded in the first wavelength range.
• the proportion of absorption in the first wavelength range is determined, which is sample-dependent and analyte-independent and is not influenced by measuring conditions.
• the sample-related change in light intensity in the first wavelength range is used to infer the sample-related change in light intensity in the second wavelength range.
• z. B. the sample-related change in light intensity in the first length range is set essentially equal to the change in sample intensity in the second length range.
• B. can be determined by extrapolation to the sample-related change in light intensity in the second wavelength range.
• the prior art measures in a first wavelength range in which the test element does not absorb or does not absorb significantly, so that a white value of the system is consequently determined.
• measurements in a first wavelength range determine the influence of the sample on the analysis result, since during the measurement an additional absorption is caused by blood dye in the sample.
• the white length range is extrapolated to the absorption of the blood pigment in the second white length range (EP-A3-0 816849).
• a black value as defined above is not taken into account in the corrections mentioned. Within the scope of the invention, however, it is possible to take into account a correction for the white value and / or the influence of the sample, as described, when correcting the measured values by the black value.
• the invention additionally relates to two methods for the detection of light intensity changes in analysis systems which are not due to analysis.
• a method includes irradiating a test element before adding the sample and detecting the light reflected or transmitted by the test element in a first wavelength range in which absorption by the dry test element takes place, which is known and not equal to zero. This absorption becomes a first Correction value determined. Subsequently, the test element is irradiated after adding the sample and detecting the light reflected or transmitted by the test element in the first wavelength range in which an analyte-independent absorption by the wet test element takes place. A second correction value is registered by means of this change in light intensity.
• the wet test element is irradiated and the light reflected or transmitted by the test element is detected in a second wavelength range in which absorption by an analyte takes place. The measurement value is thus detected.
• the first correction value is used to determine the amount of light which is registered by the detector despite essentially complete absorption of the test element. If the dry test element has essentially complete absorption in the first wavelength range, the detected correction value corresponds to the black value of the system. In the case of a previously known but essentially incomplete absorption of the dry test element, the black value is calculated using the evaluation unit.
• the second correction value represents the sum of the changes in light intensity due to the previously known absorption of the dry test element and the sample-related, analyte-independent absorption. On the basis of a differential curve from the correction values, the sample-related amount of changes in light intensity is separated from the portion due to the equipment. The analyte concentration is then determined in the second wavelength range with a correction of the measured value taking into account the black value and the sample-related absorption.
• a further method for analyzing and correcting changes in light intensity not caused by the analysis is carried out by irradiating a test element before or after adding a sample and detecting the light reflected or transmitted by the test element in a first wavelength range in which absorption takes place either by the dry test element, which is previously known and not equal to zero and is used to determine a first correction value or the absorption by the wet test element is determined to determine a second correction value.
• the first correction value is used to determine the black value.
• the second correction value additionally includes changes in light intensity that arise as a result of a sample influence.
• the test element is irradiated and the light reflected or transmitted by the test element is detected in a second wavelength range in which absorption by an analyte takes place to determine the measured value.
• the analyte concentration is determined by correcting the measured value, taking into account the first or second correction value, so that either only the black value of the method is taken into account or, in addition, the influence of the sample.
• test elements with the particular light-conducting properties shown can be used.
• the determination of a correction value in the first range of lengths is sufficient, so that the latter method is to be preferred for correcting the measured value. If this is not the case, the sample-related absorption in the first wavelength range can preferably be determined in a further method step in accordance with the first-mentioned method and used to determine the sample-related absorption in the second wavelength range.
• (I I ⁇ O / 0 ) is a theoretically expected light intensity, which results from the light emitted by the lighting unit with ideal behavior of the analysis system.
• the real detected light intensity (Iv teß ) includes a change in light intensity ( ⁇ App (i)) - which results from non-constant equipment conditions (e.g. intensity fluctuations due to ambient light, changing quality of the test strips; faulty coupling of the test strip to the lighting unit by the User; equation 2).
• I APP can be both positive and negative.
• the first correction value captures the light intensity, which is independent of the analyte and sample and cannot be absorbed a priori by the test element.
• the measured value (I mess) is equal to the correction value (i app (i)) is the measured value (I mess) is called black level.
• the black value thus reflects the minimum light intensity that is registered by the detector despite the almost complete absorption of the test element.
• the correction value (IA PP ( 2 )) includes not only changes in light intensity due to equipment, but also light intensity changes caused by the analyte-independent influence of the sample caused (e.g. absorption by sample components, change in the refractive index on the test element). If a correction value is measured exclusively on the wet test element, the measurement value (lAnalyt) is also corrected when determining an analyte concentration by subtraction analogous to equation 3.
• a first correction value is preferably determined before determining the second correction value before sample application. By forming the difference between the correction values, only the sample-related changes in light intensity in the first wavelength range can be recorded.
• a comprehensive correction of the measured value can also take a white value into account when determining an analyte concentration.
• the white value is determined in a white length range in which the test element essentially does not absorb. The white value thus reflects the maximum light intensity that is detected by the detector.
• the first correction value is first determined in the first length range. This is followed by a measurement in the second wavelength range, in which there is almost no absorption by the test element, so that the white value is registered.
• the sample is placed on the test field, a reaction of the analyte to be determined being initiated with a reagent. After the end of the reaction, measurements are again carried out in the second wavelength range, with the analyte-dependent absorption now being detected.
• the first correction value corresponds to a black value, which is independent of the sample and analyte;
• the second correction value is a black value, which is independent of the analyte.
• the difference in the black values results in the sample-related change in light intensity (Ip ro be) in the first wavelength range. From the sample-related change in light intensity in the first Wavelength range is based on the sample-related change in light intensity in the second wavelength range (Lprobe) -
• a correction value (I ⁇ 0 correction ) is determined according to equation 4.
• the invention further includes a test element with light-guiding properties for the application and analysis of samples.
• the test element contains an absorber, e.g. B. tartrazine, which has a known non-zero absorption in a first wavelength range in which there is essentially no absorption due to an analyte, which absorption is essentially complete in a preferred embodiment. There are no interactions between the substance and the sample.
• the test element contains a reagent system which reacts with the analyte of the sample in such a way that an analyte-dependent change in the absorption takes place in a second wavelength range.
• the substance absorbs in the blue white length range.
• Figure 2 Structure of an analysis system with light-conducting test element according to patent application WO 01/48464
• Figure 3 Structure of a light-conducting test element according to patent application WO 01/48464
• the analysis system 1 shown in FIGS. 1 and 2 contains a test element (2) and an evaluation device (3).
• the test element (2) is designed as a test strip (4) with an elongated carrier film (5) made of plastic and a test field (7) attached to the upper flat side (6) of the carrier film (5).
• the test element (2) is inserted through an opening (10) into the housing (11) of the evaluation device (3) into a test element holder (12) and thereby positioned in the measuring position shown in FIG. 2.
• the evaluation device (3) contains measurement and evaluation electronics 13, which in the case shown is implemented by means of a printed circuit board (14) and integrated circuits 15.
• a light transmitter (16) preferably implemented as a light-emitting diode (LED)
• a detector 17 preferably implemented as a photodiode, which are components of an optical measuring device (18).
• a drop of sample liquid (21) is applied to the side (top) of the test field (7) facing away from the carrier film (5).
• the application of the sample is facilitated by the fact that only a first section (22) of the test element (2) positioned in the measuring position is inside the housing (11), while a second section (23) with the test field (7) is out of the housing (11) protrudes and is therefore easily accessible.
• the liquid penetrates, dissolving the reagents contained in the test field (7), until it reaches the detection zone (24), which is located on the side (underside) of the test field (7) facing the carrier film (5).
• the reaction of the analyte contained in the sample with the reagent system leads to an optically measurable change, in particular a color change, in the detection zone (24).
• an optically measurable change in particular a color change
• the secondary light intensity which is diffusely reflected when the detection zone (24) is illuminated with primary light is measured. This is done by a special design of the test element (2) and the interacting parts of the optical measuring device (18).
• Figure 3 shows a test element with light-conducting elements.
• the carrier film (5) includes at least one optical light guide layer (26) with the properties explained with regard to optical transparency and refractive index. Further information on light guide elements whose light transport is based on total reflection can be found in the relevant literature (WO 01/48461).
• the carrier film (5) has two light guide layers (26), the upper light guide layer serving as a primary light guide (27) and the lower light guide layer serving as a secondary light guide (28).
• the primary light (29) is coupled by the light transmitter (16) with the aid of a lens (30) into the primary light guide (27) through its rear end face, which serves as the input surface (31) for the coupling, and within the primary light guide (27) up to the test field (7) transported.
• the part of the light path of the primary light (29) which runs inside the light guide layer (26) is referred to as the light guide section (32).
• the area of the upper flat side (6) of the light guide layer (26) which is aligned with the test field serves at least in part as a light decoupling area (33) in which the primary light (29) from the primary light guide (27) into the detection zone (24) of the Test field (7) is coupled out.
• the primary light (29) is essentially decoupled by the fact that the lower flat side of the carrier film (5) opposite the decoupling region (33) (also also the test field (7)) (in the two-layer embodiment of the carrier film shown, the lower flat side of the primary light guide (27)) is designed such that the primary light is deflected into the detection zone (24) of the test field (7).
• This change in the direction of light propagation is brought about by a reflecting surface (25) which is preferably inclined at an angle of approximately 45 °. They should be polished and / or provided with a shiny metallic coating to improve their reflective properties. Deviations from the angle of 45 ° are possible.

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• 2001
  • 2001-12-22 DE DE10163775A patent/DE10163775A1/de not_active Ceased
• 2002
  • 2002-12-19 US US10/499,252 patent/US7758812B2/en active Active
  • 2002-12-19 AU AU2002367206A patent/AU2002367206A1/en not_active Abandoned
  • 2002-12-19 JP JP2003556789A patent/JP2005513498A/ja active Pending
  • 2002-12-19 CA CA002470862A patent/CA2470862A1/en not_active Abandoned
  • 2002-12-19 WO PCT/EP2002/014534 patent/WO2003056314A2/de not_active Ceased
  • 2002-12-19 EP EP02805760A patent/EP1461603A2/de not_active Withdrawn

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