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Optimization of prothrombin time measurements in canine plasma
Objective:
To optimize a prothrombin time (PT) method designed for human plasma for use with canine plasma.
Sample Population:
100 plasma samples from healthy dogs and 50 plasma samples with reduced activity of the single factors II, V, VII or X.
Procedure:
Canine plasma samples with various coagulation activity values (100, 75, 50, 25 and 10%: prepared by dilution from a plasma pool [n = 100]) were assayed at various sample dilutions and dilutions of the thromboplastin component of 3 commercial calcium thromboplastin reagents. The sc-named optimized PT test was compared with the standard test with respect to its sensitivity and correlation with the sum of the activity decreases of single factors II, V, VII, and X in relation to the respective reference range.
Results:
The time intervals between various coagulation activity values, which were small by use of the standard test, could be increased by diluting the sample and substituting fibrinogen, but not by diluting the tissue thromboplastin component of PT reagent. On the basis of 50 abnormal plasma samples, the optimized test had high sensitivity (0.90 to 1.00, dependent on reagent and sample dilution) in contrast to the standard test, which had low sensitivity (0.24 to 0.58, dependent on reagent). Also, correlation with the sum of the activity decreases was closer by use of the optimized (0.90 to 0.93) than the standard (0.58 to 0.84) test.
Conclusions:
In contrast to the standard test, an optimized test is suitable as a sensitive screening test of the extrinsic coagulation system in dogs.
Clinical Relevance:
The optimized PT method is easy to perform and, therefore, should be in general use for assay of canine plasma.