WO2017106334A1

WO2017106334A1 - Methods, kits and systems for screening for sickle-cell disease

Info

Publication number: WO2017106334A1
Application number: PCT/US2016/066641
Authority: WO
Inventors: Frank A. FERRONE; Alexey M. APRELEV
Original assignee: Drexel University
Current assignee: Drexel University
Priority date: 2015-12-18
Filing date: 2016-12-14
Publication date: 2017-06-22
Anticipated expiration: 2018-06-18

Abstract

One aspect of the invention provides a method of screening for sickle-cell disease. The method includes: contacting an end of a capillary tube with deoxygenated blood; observing a flow rate of the deoxygenated blood within the capillary tube; and performing one or more steps selected from the group consisting of: comparing the flow rate to a predetermined flow-rate threshold for the capillary tube indicative of sickle-cell disease; calculating viscosity based on the flow rate and comparing the viscosity to a predetermined viscosity threshold for the capillary tube indicative of sickle-cell disease; and comparing the flow rate to a second flow rate for oxygenated blood from a same subject within a substantially identical capillary tube.

Description

METHODS, KITS, AND SYSTEMS FOR SCREENING FOR SICKLE-CELL DISEASE

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to US Provisional Patent Application Serial

No. 62/269,571, filed December 18, 2015. The entire content of this application is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

Sickle cell disease is a genetic condition that causes deoxygenated hemoglobin in red blood cells to assemble into rigid polymers. The flexibility of cells-essential for cell traversal of the capillary bed-is thus destroyed.

Due to its nature as a genetic disorder, sickle cell disease continues to be present in significant numbers of people throughout the world. In the US, life-span has been extended thanks to early and regular care, despite the fact that only one drug is available. While median life span for the 100,000 sickle patients in the US is around 40 years, it is less than 5 years in Africa, where it is estimated by the WHO that 300,000 new cases arise yearly.

SUMMARY OF THE INVENTION

This aspect of the invention can have a variety of embodiments. The capillary tube can be unobstructed. The capillary tube and the substantially identical capillary tube can be unobstructed.

The blood can have been deoxygenated through the use of a chemical reductant.

The flow rate of deoxygenated sickle-cell blood can be slower than that of oxygenated sickle-cell blood. Deoxygenated sickle-cell blood can be more viscous than oxygenated sickle- cell blood. The flow rate of deoxygenated healthy blood can be equal to that of oxygenated healthy blood. Deoxygenated healthy blood can have the same viscosity as oxygenated healthy blood. The flow rate of deoxygenated sickle trait blood can resemble the flow rate of deoxygenated healthy blood immediately after deoxygenation and more closely resemble the flow rate of deoxygenated sickle-cell blood as time after deoxygenation increases.

The capillary tube can have a volume of about 0.25 μΐ_^.

Another aspect of the invention provides a method of screening for sickle-cell disease. The method includes: contacting an end of a capillary tube with oxygenated blood, wherein the capillary tube is adapted and configured to deoxygenate the oxygenated blood to produce deoxygenated blood; observing a flow rate of the deoxygenated blood within the capillary tube; and performing one or more steps selected from the group consisting of: comparing the flow rate to a predetermined flow-rate threshold for the capillary tube indicative of sickle-cell disease; calculating viscosity based on the flow rate and comparing the viscosity to a predetermined viscosity threshold for the capillary tube indicative of sickle-cell disease; and comparing the flow rate to a second flow rate for oxygenated blood from a same subject within a substantially identical capillary.

The capillary tube can have a volume of about 0.25 μΐ_^. The capillary tube can be glass capillary tube.

Another aspect of the invention provides a system for rapidly screening for sickle-cell disease. The system includes: a capillary assembly including two or more capillary tubes having identical composition and dimensions and each having two open ends; and a connecting body coupled to the two or more capillary tubes. The connecting body holds the two or more capillary tubes parallel to each other in an array wherein each tube is a defined distance from each neighboring tube.

This aspect of the invention can have a variety of embodiments. The system can further include a handle coupled to the connecting body.

The system can further include a sample container adapted and configured to hold two or more liquid samples in designated locations such that the designated locations are oriented in an array complementarily aligned with the array of the two or more capillary tubes, such that the two or more capillaries can simultaneously contact the two or more liquid samples. The sample container can be a flat surface. The designated locations can be markings on the flat surface. The sample container can be a piece of glass. The designated locations can be wells adapted and configured to hold the two or more liquid samples.

The sample container can further include a strong reducing agent capable of

deoxygenating one or more of the two or more liquid samples. The sample container can further include one or more oxygen permeable materials. The sample container can further include one or more materials selected from the group consisting of polydimethylsiloxane, poly(methyl methacrylate), silicone rubber, polyurethane, polyethylene, amorphous fluoropolymers, and liquid crystal polymers.

The system can further include one or more pipettes for transferring the two or more liquid samples to the sample container. The one or more pipettes can include one or more oxygen permeable materials. The one or more pipettes can include one or more materials selected from the group consisting of polydimethylsiloxane, poly(methyl methacrylate), silicone rubber, polyurethane, polyethylene, amorphous fluoropolymers, and liquid crystal polymers. The one or more of the pipettes can include a strong reducing agent capable of deoxygenating one or more of the two or more liquid samples.

The system can further include a robotic arm.

The two or more capillary tubes can be unobstructed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing figures wherein like reference characters denote corresponding parts throughout the several views.

FIG. 1 depicts a method of screening for sickle-cell disease according to an embodiment of the invention.

FIGS. 2A-2F depict capillaries and systems according to embodiments of the invention.

FIG. 3 A depicts the relationship between viscosity of a blood sample and the hematocrit (fraction of red blood cells) of the blood sample.

FIG. 3B depicts the rate of ascent of blood samples up a capillary as a function of time for both oxygenated and deoxygenated blood samples comprising a 95:5 SS : AA blood ratio.

FIG. 4 A depicts the rise times of oxygenated vs. deoxygenated blood samples having varying traits using a vertical capillary system.

FIG. 4B depicts ratios of deoxygenated rise times to oxygenated rise times using a vertical capillary system.

FIGS. 5A and 5B depict displacement over time for oxygenated vs. deoxygenated blood samples having varying traits.

FIG. 6 depicts the effect of sodium dithionite on blood flow.

FIG. 7 depicts the delay in rigidification of blood cells in an AS blood sample in comparison to an SS blood sample.

FIGS. 8A-8C depict the rise times of oxygenated vs. deoxygenated blood samples for sickle cell (8A), healthy (8B) and sickle trait (8C) blood.

FIGS. 9A-9J depict the run-through times of oxygenated vs. deoxygenated blood samples having varying traits using a horizontal capillary system.

DEFINITIONS

The instant invention is most clearly understood with reference to the following definitions.

As used herein, the singular form "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

Unless specifically stated or obvious from context, as used herein, the term "about" is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about.

As used in the specification and claims, the terms "comprises," "comprising,"

"containing," "having," and the like can have the meaning ascribed to them in U.S. patent law and can mean "includes," "including," and the like.

Unless specifically stated or obvious from context, the term "or," as used herein, is understood to be inclusive.

Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 (as well as fractions thereof unless the context clearly dictates otherwise).

The following abbreviations are used herein:

AA phenotypically normal blood

AS sickle trait blood

PDMS polydimethylsiloxane

PMMA poly(methyl methacrylate)

SC blood heterozygous for hemoglobin S (HbS) and hemoglobin C (HbC) SS sickle cell disease blood

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the invention provide methods for screening for sickle-cell disease. Without being bound by theory, it is believed that deoxygenated sickle cells are more rigid than oxygenated sickle cells, which influences the viscosity of deoxygenated sickle blood relative to oxygenated sickle blood. In contrast, there should be little or no difference in the viscosity of between deoxygenated non-sickle blood relative to oxygenated non-sickle blood.

Advantageously, aspects of the invention facilitate detection of sickle-cell disease without the use of obstructed capillaries.

Referring now to FIG. 1, one aspect of the invention provides a method 100 of screening for sickle-cell disease. In step SI 02, an end of a capillary tube is contacted with blood. The capillary tube can be unobstructed so that pressure does not increase above the blood drawn into the capillary. For example, the capillary can be free from the beads disclosed in International Publication No. WO 2015/054378.

In some embodiments, the blood was previously deoxygenated. For example, a reducing agent such as a dithionite, e.g., sodium dithionite (Na₂S₂0₄) can be added to the blood prior to contact with the capillary tube. In another example, the blood is placed on an oxygen-permeable substrate or within an oxygen-permeable vessel. Suitable oxygen-permeable materials include soft polymers such as poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS), silicone rubber, polyurethane, polyethylene, amorphous fluoropolymers (available, e.g., under the TEFLON® AF trademark from The Chemours Company of Wilmington, Delaware), and liquid crystal polymers available, e.g., under the VECTRA® trademark from CNA Holdings LLC of Irving, Texas).

In other embodiments, the blood is oxygenated blood that is subsequently deoxygenated within the capillary tube. The capillary tube can include a variety of features to facilitate deoxygenation.

In one embodiment, the capillary tube includes a reducing agent. For example, the reducing agent can be dried to an interior wall of the capillary tube such as in U.S. Patent No. 4,308,029. All or a portion of the capillary tube can be modified to increase the reducing- agent-carrying capacity. For example, all or a portion of the capillary tube can be etched with an acid. In another example, all or a portion of the capillary tube can have a non-cylindrical cross- section (e.g., triangular, square, n-gon, and the like) to provide increased surface area for the dried reducing agent to attach.

In another embodiment, the capillary includes at least an oxygen-permeable portion that will draw oxygen from the blood. A comparison can be made between flow of blood that is deoxygenated by the oxygen-permeable portion and a control tube that has the same structure, but is saturated with oxygen prior to introduction of the sample (e.g., by flowing oxygen through the capillary prior to introduction of the sample).

In step SI 04, a flow rate of the deoxygenated blood within the capillary tube is measured. The flow rate can measured optically, e.g., by calculating the time required for the blood to travel a distance (e.g., between a first point and a second point) within the capillary tube. The measurements can be made by eye or can be automated using a camera (e.g., a digital camera) and software including instructions to detect movement of blood within the capillary across a plurality of images or frames within a video.

In steps SI 06, SI 08, and SI 10, the measurement of the flow rate of the deoxygenated blood can be interpreted using one or more approaches.

In step SI 06, the calculated flow rate of the deoxygenated blood can be compared to a predetermined flow-rate threshold for the capillary tube indicative of sickle-cell disease. For example, clinical data can be used to establish a range of flow rates indicative of sickle-cell disease for a particular capillary tube having a defined material and cross-section.

In step SI 08, the viscosity of the deoxygenated blood can be calculated. The rise of the blood through the capillary tube can be modeled by deriving an equation from Poiseuille's equation governing the flow of viscous liquids through small tubes. Applicant derived the following equation for the height of the liquid, denoted L, at time t after the blood is introduced at the bottom of the tube:

-ⁱ - ^{z ta} (ⁱ - ) = i

where Z is the Jurin length and τ is the characteristic time. The Jurin length Z is defined by

2 (7 CO s Θ

Z = in which σ is the surface tension, Θ is the contact angle, p is the blood density, g is the acceleration of gravity, and r is the radius of the capillary. The characteristic time includes the viscosity as well, and is given by τ = -—^ in which η is the viscosity and the other symbols are as defined above. Therefore the characteristic time is proportional to the viscosity. This viscosity can then be compared to a predetermined viscosity threshold for the capillary tube indicative of sickle-cell disease.

In step SI 10, the flow rate can be compared to a second flow rate for oxygenated blood from a same subject within a substantially identical capillary. The comparison can be under a race condition in which both two capillaries are contacted blood samples at the same time and a user or a device detects which blood sample reaches a defined point first. In other embodiment, the flow rate is separately measured and then numerically compared to determine whether a difference exists. For example, the two flow rates can be compared to determine if one flow rate is higher than the other, one flow rate can be subtracted from the other, or one flow rate can be divided by the other. FIGS. 2A-2C depict cross-sections of various embodiments of capillaries.

The capillary tube 202a-c can be a cylinder having a sufficiently small cross-section to induce capillary or wicking flow of a fluid into the capillary tube 202a-c. For example, the cylinder can have a largest cross-sectional dimension of about 5 mm, about 4 mm, about 3 mm, about 2 mm, about 1 mm, and the like. For example, capillary tube 202a-c can have a circular, rectangular, or square cross-section. Capillary tubes fabricated from materials such as borosilicate, clear fused quartz, and synthetic fused silica are commercially available from sources such as VitroCom of Mountain Lake, New Jersey and Drummond Scientific Company of Broomall, Pennsylvania. For example, VitroCom offers capillary tubes having circular cross- sections with internal diameters (IDs) of 0.05 mm, 0.10 mm, 0.15 mm, 0.20 mm, 0.30 mm,

0.40 mm, 0.50 mm, 0.60 mm, 0.70 mm, 0.80 mm, 0.90 mm, 1.00 mm, 1.50 mm, 2.00 mm, and the like and lengths of 100 mm, 300 mm, 600 mm, and the like. Capillary tubes 202a can be selected so that the anticipated blood samples will not wick through to the other end of the capillary tube 202a-c or can be selected so that the exit of the blood sample at an opposite end of the capillary tube 202a-c marks an end point of the measurement.

FIG. 2A depicts a capillary that can be fabricated from a variety of materials such as glass or soft polymers such as PMMA.

FIG. 2B depicts a capillary 202b including a dried reducing agent 204 at a first end of the capillary. The dried reducing agent can optionally extend the entire length of the capillary 202b, although partial coverage may preferred so that movement of the blood sample within the capillary 202b can be more clearly visualized and will reflect blood-capillary interactions instead of blood-reducing-agent interactions.

The capillary 202b of FIG. 2B can be provided in a control version that includes an equivalent (e.g., by mass, volume, molar volume, and the like) amount of a non-reducing salt to facilitate control comparisons of the blood samples that are not deoxygenated.

FIG. 2C depicts a capillary 202c including at least one oxygen-permeable portion 206. The oxygen-permeable portion 206 can be mechanically or chemically bonded to on oxygen- impermeable portion 208 of the capillary 202c.

Embodiments of the invention can be implemented in systems and/or kits. For example, kits can be provided including capillaries and/or reducing agents (e.g., reducing agents dried within capillaries). The kits can also include instructions for performing the methods described herein.

Systems can include devices for holding the capillaries and/or measuring blood flow within the capillary, calculating flow rates within the capillary, comparing blood flow and/or viscosity between samples, and/or conveying a diagnosis.

FIGS. 2D and 2E depict a capillary system of the invention 210, demonstrating the main principle of the invention, wherein deoxygenated sickle cell disease or sickle cell trait blood has a slower flow rate through a capillary than oxygenated sickle cell disease or sickle cell trait blood.

Referring now to FIG. 2D, the system of the invention can include a sample slide 212 adapted and configured for holding one or more blood samples 214, 216.

The substrate 212 can be configured to configured to complement the capillary assembly.

For example, the substrate can include one or more markings corresponding to the spatial arrangement of the capillaries 202. These markings can direct the user to approximate targets for depositing blood samples. Likewise, the substrate 212 can define a plurality of wells having a complementary special relationship to the capillaries. (In some embodiments, the capillary assembly can be configured for compatibility with various commercially available well plates.)

In another example, the substrate 212 can be configured to facilitate deoxygenation of one of the blood samples (e.g., through the use of salts or materials as described herein in the context of capillary design).

The one or more blood samples 214, 216 can include an oxygenated blood sample 214 and/or a deoxygenated blood sample 216.

A capillary assembly 218 including a plurality of capillaries 202a-c can facilitate the handling of the one or more capillaries 202a-c for simultaneous or substantially simultaneous contact with blood samples 214, 216. The apparatus 218 can include a handle 220 or other structure to facilitate handling of the capillary assembly 218 (e.g., by a technician's hands, with tools such as forceps, by a robotic device, and the like).

Referring now to FIGS. 2D and 2E, system 210 can facilitate rapid qualitative

comparison between oxygenated blood samples and deoxygenated blood samples. The system 210 can enable two identical capillaries 202a to be individually dipped into an oxygenated blood sample 214 and a deoxygenated blood sample 216 on a sample slide 212 simultaneously, such that the sample slide 212 is substantially horizontal and the capillaries 202a are dipped into the blood samples such that they are in a substantially vertical orientation, perpendicular to the sample slide 212. A comparison can then be made between the flow rate of the oxygenated blood sample 214 and the deoxygenated blood sample 216 by comparing the oxygenated blood level 222 and the deoxygenated blood level 224 through the respective capillaries 202a at a given time point.

Referring now to FIG. 2F, other embodiments of the invention provide assemblies 226 including one or more sample wells 228 adapted and configured to hold a blood sample and one or more capillaries 202a-c. The capillaries 202 and sample wells 226 can lie horizontally. The assembly 226 can be a a plastic mold defining and/or housing the sample wells 228 and the capillaries 202. The assembly 226 can include a capillary 202c including at least one oxygen- permeable portion 206, which allows for in situ deoxygenation of a blood sample. In other embodiments, an oxygen reducing agent can be present in one or more sample wells 226 or deoxygenation can occur before introduction of a blood sample into the well(s) 226.

WORKING EXAMPLES

Procedure

Typical Single Capillary Experiments

0.25uL glass DRUMMOND® capillaries were marked with a permanent marker at 1 cm from the top end of the capillary. This was the "Start" mark and the "Finish" was at the top of the capillary. Two vials of blood were prepared: one vial contained oxygenated blood, while the other contained deoxygenated blood with an appropriate amount of sodium-dithionite-water solution (usually 1-2 ^χ the amount calculated to strip all the oxygen so as to safeguard against partially compromised dithionite). The spectrum of each vial sample was obtained and recorded. The capillary was fitted into an eye-drop holder so as to better handle it. 2-5 μΙ_, of blood from the oxygenated blood vial was pipetted onto a glass slide coverslip. The capillary was then held at a 50-60° angle relative to the surface, and dipped into the blood droplet. A stopwatch was used to measure the time required for the blood to travel the distance from the first mark to the top. This time was recorded. The trial was repeated four times with a fresh capillary and droplet of blood for a total of five trials. The process was repeated for blood from the deoxygenated vial, measuring the capillaries' spectra after each trial to verify deoxygenation.

Parallel Capillary Experiment

Two capillaries were prepared as above and placed into a pair of eye-droppers that were attached together. The marks were lined up relative to one another. A 5 μΙ_, drop of oxygenated blood was placed onto a glass slide coverslip, and, after changing the glass pipette, a 5 μΙ_, drop of deoxygenated blood was placed next to the oxygenated drop such that one capillary contacted the oxygenated blood sample and the other capillary contacted the deoxygenated blood sample.

The capillaries were then dipped simultaneously into the drops. Visual inspection determined which capillary ran faster. With a stopwatch, the deoxygenated capillary was timed between marks. Spectra of each capillary was then measured and recorded.

Capillary-Based Deoxygenation

A I M sodium dithionite solution was prepared, pulled into a capillary and then expelled, and the tube dried by passing nitrogen gas through the capillary tube. Once dry, the tube was used to aspirate a few iL of blood, and expel it back onto a slide. In doing so, the blood deoxygenates in the capillary (as verified by direct measurement). The drops of blood on a slide can be then used like the blood in the vial, above.

Results

Referring to FIGS. 4A-4E, the method differentiates strongly between oxygenated and deoxygenated samples in SS and sickle variants. Tested were SS (pure sickle blood), AS (sickle trait), SC (a patient heterozygous for hemoglobin S (HbS) and hemoglobin C (HbC)), and SP° thalassemia. Also shown are normal (AA) blood, and sickle blood from a patient that was exchange-transfused, which could have 30% or more normal blood from the exchange. In AA and SS blood that was exchange-transfused (marked T), there was statistically no difference between oxygenated and deoxygenated samples. Error bars reported here are one standard deviation using the Student-T distribution.

Capillary Displacement Curves

Referring to FIGS. 5A and 5B, Applicant used video capture to examine in detail the dynamics of sample mixtures of SS and AA blood rising up a 0.25 iL capillary. The goal of this mixing experiment was to study the sensitivity of the method and its potential use as a severity diagnostic. Because the AA and SS blood had different hematocrits, Applicant created mixtures that increased the overall hematocrit of the mixture, but decreased the percentage of sickling cells as the mixtures progress.

Sodium dithionite causes a change in the behavior of the cells. Whereas one would expect exact parity for 0% SS between oxygenated and deoxygenated samples, the deoxygenated samples proceed faster. This is not because the red blood cells are deoxygenated, but because of the dithionite, as shown below in FIG. 6.

Blood exposed to oxygen or CO behaves identically as shown above in red and blue legends. Dithionite, while it reduces oxygen, does not affect CO. The green curves are replicates of blood with CO and dithionite, which runs faster than the CO sample without dithionite.

Differentiation of SS and AS Blood

The kinetics of the polymerization of hemoglobin generate a time delay between deoxygenation and the rigidification/sickling of the cell for SS and AS blood. Because this delay time for AS is much greater than that of SS, a second measurement allows a significant portion of AS cells to sickle and rigidify, increasing its viscosity. This feature allows for the distinction between an AS sample and an AA sample. The time delay can be seen in the results reported in FIG. 7, wherein the number of sickled cells is measured as a function of scattering intensity.

Referring to FIGS. 8A-8C, this principle allows for distinction between AA, AS and SS samples by comparing the flow rate of an oxygenated sample with two deoxygenated samples taken at different time points. As can be seen in FIG. 8A, the change in flow rate of oxygenated and deoxygenated SS blood is apparent at both early and later time points. FIG. 8B demonstrates that there is no change in the flow rate of oxygenated and deoxygenated AA blood, regardless of the time the deoxygenated blood was tested. FIG. 8C, however, shows that while there is no significant difference in the flow rate of oxygenated and deoxygenated AS blood for early deoxygenation measurements, similar to AA blood, later deoxygenation measurements, after the AS blood has been given time to undergo rigidifi cation, exhibits a much slower flow rate.

Results

Referring to FIGS. 9A-9J, the horizontal capillary device also differentiates strongly between oxygenated and deoxygenated samples in SS and sickle variants. Shown are results from normal (AA) blood (9 A, 9B), AS (sickle trait) (9C, 9D), SC (a patient heterozygous for HbS and HbC) (9E, 9F), SS (pure sickle blood) (9G, 9H), SS(HU) (pure sickle blood from a patient treated with hydroxyurea) (91), and SS(transfused) (pure sickle blood which has been exchange transfused) (9 J). Blood was deoxygenated using dithionite and was added to the horizontal capillary device quickly in all tests barring the experiment reported in FIG. 9G. AA blood showed no statistical difference between oxygenated and deoxygenated samples while AS, SC and SS blood showed varying degrees of difference between oxygenated and deoxygenated samples. Additionally, it was found that SS blood which had been deoxygenated using dithionite and used quickly exhibited similar flow rates with SS blood which had been allowed to stir with dithionite for an extended period of time (FIGS. 9G, 9H).

EQUIVALENTS

Although preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

INCORPORATION BY REFERENCE

The entire contents of all patents, published patent applications, and other references cited herein are hereby expressly incorporated herein in their entireties by reference.

Claims

1. A method of screening for sickle-cell disease, the method comprising:

contacting an end of a capillary tube with deoxygenated blood;

observing a flow rate of the deoxygenated blood within the capillary tube; and performing one or more steps selected from the group consisting of:

comparing the flow rate to a predetermined flow-rate threshold for the capillary tube indicative of sickle-cell disease;

calculating viscosity based on the flow rate and comparing the viscosity to a predetermined viscosity threshold for the capillary tube indicative of sickle-cell disease; and

comparing the flow rate to a second flow rate for oxygenated blood from a same subject within a substantially identical capillary tube.

2. The method of claim 1, wherein the capillary tube is unobstructed.

3. The method of claim 1, wherein the capillary tube and the substantially identical capillary tube are unobstructed.

4. The method of claim 1, wherein the blood has been deoxygenated through the use of a chemical reductant.

5. The method of claim 1, wherein the flow rate of deoxygenated sickle-cell blood is slower than that of oxygenated sickle-cell blood.

6. The method of claim 1, wherein deoxygenated sickle-cell blood is more viscous than oxygenated sickle-cell blood.

7. The method of claim 1, wherein the flow rate of deoxygenated healthy blood is equal to that of oxygenated healthy blood.

8. The method of claim 1, wherein deoxygenated healthy blood has the same viscosity as oxygenated healthy blood.

9. The method of claim 1, wherein the flow rate of deoxygenated sickle trait blood resembles the flow rate of deoxygenated healthy blood immediately after deoxygenation and more closely resembles the flow rate of deoxygenated sickle-cell blood as time after

deoxygenation increases.

10. The method of claim 1, The method of claim 1, wherein the capillary tube has a volume of about 0.25 μΐ_^.

11. A method of screening for sickle-cell disease, the method comprising:

contacting an end of a capillary tube with oxygenated blood, wherein the capillary tube is adapted and configured to deoxygenate the oxygenated blood to produce deoxygenated blood; observing a flow rate of the deoxygenated blood within the capillary tube; and performing one or more steps selected from the group consisting of:

comparing the flow rate to a second flow rate for oxygenated blood from a same subject within a substantially identical capillary.

12. The method of claim 11, wherein the capillary tube is unobstructed.

13. The method of claim 11, wherein the capillary tube and the substantially identical capillary tube are unobstructed.

14. The method of claim 11, wherein the flow rate of deoxygenated sickle-cell blood is slower than that of oxygenated sickle-cell blood.

15. The method of claim 11, wherein deoxygenated sickle-cell blood is more viscous than oxygenated sickle-cell blood.

16. The method of claim 11, wherein the flow rate of deoxygenated healthy blood is equal to that of oxygenated healthy blood.

17. The method of claim 11, wherein deoxygenated healthy blood has the same viscosity as oxygenated healthy blood.

18. The method of claim 11, wherein the flow rate of deoxygenated sickle trait blood resembles the flow rate of deoxygenated healthy blood immediately after deoxygenation and more closely resembles the flow rate of deoxygenated sickle-cell blood as time after

deoxygenation increases.

19. The method of claim 11, wherein the capillary tube has a volume of about 0.25 [iL.

20. The method of claim 11, wherein the capillary tube is glass capillary tube.

21. A system for rapidly screening for sickle-cell disease, the system comprising:

a capillary assembly comprising two or more capillary tubes having identical composition and dimensions and each having two open ends; and

a connecting body coupled to the two or more capillary tubes, the connecting body holding the two or more capillary tubes parallel to each other in an array wherein each tube is a defined distance from each neighboring tube.

22. The system of claim 21, further comprising:

a handle coupled to the connecting body.

23. The system of claim 21, further comprising:

a sample container adapted and configured to hold two or more liquid samples in designated locations such that the designated locations are oriented in an array complementarily aligned with the array of the two or more capillary tubes, such that the two or more capillaries can simultaneously contact the two or more liquid samples.

24. The system of claim 23, wherein the sample container is a flat surface.

25. The system of claim 24, wherein the designated locations are markings on the flat surface.

26. The system of claim 24, wherein the sample container is a piece of glass.

27. The system of claim 23, wherein the designated locations are wells adapted and configured to hold the two or more liquid samples.

28. The system of claim 23, wherein the sample container comprises a strong reducing agent capable of deoxygenating one or more of the two or more liquid samples.

29. The system of claim 23, wherein the sample container comprises one or more oxygen permeable materials.

30. The system of claim 29, wherein the sample container comprises one or more materials selected from the group consisting of polydimethylsiloxane, poly(methyl methacrylate), silicone rubber, polyurethane, polyethylene, amorphous fluoropolymers, and liquid crystal polymers.

31. The system of claim 23, further comprising one or more pipettes for transferring the two or more liquid samples to the sample container.

32. The system of claim 21, wherein the one or more pipettes comprise one or more oxygen permeable materials.

33. The system of claim 32, wherein the one or more pipettes comprises one or more materials selected from the group consisting of polydimethylsiloxane, poly(methyl

methacrylate), silicone rubber, polyurethane, polyethylene, amorphous fluoropolymers, and liquid crystal polymers.

34. The system of claim 21, wherein the one or more of the pipettes comprises a strong reducing agent capable of deoxygenating one or more of the two or more liquid samples.

35. The system of any one of claims 21-34, further comprising:

a robotic arm.

36. The system of any one of claims 21-34, wherein the two or more capillary tubes are unobstructed.