INFLUENCE OF SAMPLE PREDILUTION ON THE SENSITIVITY OF PROTHROMBIN TIME IN FELINE PLASMA

The prothrombin time (PT) is measured in feline plasma usually by mean s of a method that has been optimized for measurements in human plasma (standard test). In the present study the sensitivity of this test wa s investigated in comparison to a modified PT using a human placental thromboplastin. In the modified test, 100 mu l sample predilution (1:5 , 1:10, and 1:20) were incubated with 100 mu l of a human fibrinogen s olution (2 g/l) until 100 mu l Ca-thromboplastin was added. When measu red in 31 samples with a reduced, and 22 samples with an increased act ivity of the coagulation factors II, V, VII and/or X the modified rest showed an increased sensitivity as well as a correlation between PT a nd the changes in single factor activity which was distinctly closer c ompared to the standard test. The highest sensitivity was produced by a 1:10 or 1:20 sample dilution. A rest procedure modified in this way, is thus, a more reliable screening test for the extrinsic system in c ats and should be used for routine diagnostics.