NMR detection of coagulation time
The invention relates to detecting coagulation and coagulation-related activities including agglutination and fibrinolysis of samples. More particularly the invention relates to methods and apparatus for monitoring coagulation and/or obtaining a coagulation time of a sample using NMR-based detectors.
1. A method for determining the coagulation time of a sample obtained from a test subject, comprising:
(a) providing a sample from a test subject;
(b) mixing a coagulation reagent with said sample to initiate coagulation;
(c) measuring T 2 relaxation times of the sample in a carrier within a detection volume of an NMR detector of an NMR device using a CPMG sequence characterized by an inter-echo delay of between 0.2 milliseconds and 2 milliseconds and a dwell time of between about 1 second and about 6 seconds to determine at least two values of T 2 of the sample within about 10 seconds of performing step (b, wherein the T 2 is responsive to the extent of coagulation; and
(d) based upon the results of step (c), determining a value for the sample, wherein the value is the coagulation time of the sample or an NMR parameter characteristic of the coagulation time of the sample.
2. The method of claim 1 , wherein the value of step (d) is calculated from (i) the overall change of T 2 over time, (ii) the rate of T 2 change over time, (iii) the coagulation time determined from T 2 change, (iv) the fluctuation of T 2 change in the sample prior to coagulation, or (v) the T 2 coagulation-time-curve.
3. The method of claim 1 , wherein the sample is normal plasma, normal blood, or a fraction of normal blood.
4. The method of claim 1 , wherein
a) the coagulation reagent is mixed with the sample prior to the test carrier being placed within the detection volume of the NMR detector;
b) the coagulation reagent is mixed with the sample after the test carrier is placed within the detection volume of the NMR detector;
c) the sample is placed within the test carrier prior to the test carrier being placed within the detection volume of the NMR detector; and/or
d) the sample is placed within the test carrier after the test carrier is placed within the detection volume of the NMR detector.
5. The method of claim 1 , wherein the T 2 is measured before the sample is coagulated.
6. The method of claim 1 , wherein the coagulation time is determined as a difference between an end time and a start time, wherein coagulation substantially started at the start time and substantially ended at the end time.
7. The method of claim 6 , wherein the start time is the time at which a coagulation reagent that induces or supports coagulation is mixed with the sample under conditions suitable for the coagulation reagent to induce or support coagulation in the sample, and the end time is associated with a value of T 2 that does not substantially differ from any subsequent value of T 2 .
8. The method of claim 1 , wherein the CPMG sequence is characterized by a recycle delay of about 1 second.
9. The method of claim 1 , wherein the CPMG sequence is characterized by a number of acquired echoes of between 500 and 2,000.
10. The method of claim 1 , wherein the CPMG sequence is characterized by an inter-echo delay of about 0.5 milliseconds.
11. The method of claim 1 , wherein the CPMG sequence is characterized by a dwell time of about 4.5 or about 5.5 seconds.
12. The method of claim 1 , wherein the coagulation reagent is a prothrombin time coagulation reagent, and step (d) comprises determining the prothrombin time of the sample or an NMR parameter characteristic of the prothrombin time of the sample.
13. The method of claim 12 , wherein the prothrombin time of an abnormal sample is about 67 seconds.
14. The method of claim 12 , wherein the prothrombin time of a normal sample is about 19 seconds.
15. The method of claim 1 , wherein the coagulation reagent is an activated partial thromboplastin time coagulation reagent, and step (d) comprises determining the activated partial thromboplastin time of the sample or an NMR parameter characteristic of the activated partial thromboplastin time of the sample.
16. The method of claim 14 , wherein the activated partial thromboplastin time for a normal sample is about 70 seconds or about 50 seconds.
17. The method of claim 14 , wherein the activated partial thromboplastin time for an abnormal sample is about 140 seconds or about 90 seconds.
18. The method of claim 1 , wherein the coagulation reagent is a partial thromboplastin time coagulation reagent, and step (d) comprises determining the partial thromboplastin time of the sample or an NMR parameter characteristic of the partial thromboplastin time of the sample.
19. The method of claim 1 , wherein the coagulation reagent is a thrombin clotting time coagulation reagent, and step (d) comprises determining the thrombin clotting time of the sample or an NMR parameter characteristic of the thrombin clotting time of the sample.
20. The method of claim 1 , wherein the coagulation reagent is a fibrinogen reagent, and step (d) comprises determining the fibrinogen assay clotting time of the sample or an NMR parameter characteristic of the fibrinogen assay clotting time of the sample.
21. The method of claim 1 , wherein the coagulation reagent is an activated clotting time reagent, and step (b) comprises determining a value for the sample, wherein the value is the activated clotting time of the sample or an NMR parameter characteristic of the activated clotting time of the sample.
22. The method of claim 1 , further comprising, on the basis of step (d), determining whether the coagulation time is normal or abnormal.
23. The method of claim 22 , further comprising, when the coagulation time is abnormal, administering to the subject a coagulant or an anticoagulant.