OPTIMIZATION OF PROTHROMBIN TIME MEASUREMENTS IN CANINE PLASMA

Objective-To optimize a prothrombin lime (PT) method designed for huma n plasma for use with canine plasma. Sample Population-200 plasma samp les from healthy dogs and 50 plasma samples with reduced activity of t he single factors II, V, VII or X. Procedure-Canine plasma samples wit h Various coagulation activity Values (100, 75, 50, 25 and 10%: prepar ed by dilution from a plasma pool [n = 100]) were assayed at various s ample dilutions and dilutions of the thromboplastin component of 3 com mercial calcium thromboplastin reagents. The so-named optimized PT tes t was compared with the standard test with respect to its sensitivity and correlation with the sum of the activity decreases of single facto rs II, V, VII, and X in relation to the respective reference range. Re sults-The time intervals between various coagulation activity values, which were small by use of the standard test, could be increased by di luting the sample and substituting fibrinogen, but not by diluting the tissue thromboplastin component of PT reagent. On the basis of 50 abn ormal plasma samples, the optimized test had high sensitivity (0.90 to 1.00, dependent on reagent and sample dilution) in contrast to the st andard test, which had low sensitivity (0.24 to 0.58, dependent on rea gent). Also, correlation with the sum of the activity decreases was cl oser 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 optimize d test is suitable as a sensitive screening test of the extrinsic coag ulation 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.