Sensitivity of commercial prothrombin time reagents to detect coagulation factor deficiencies in equine plasma.
The sensitivity of commercial prothrombin time (PT) tests was assessed based on a dilution series of equine pooled plasma (EPP) (experiment 1) and on 40 equine plasma samples with reduced activity of coagulation factors II, V, VII and X (experiment 2). Two different PT reagents (reagent 1, human placental thromboplastin; reagent 2, recombinant human tissue factor) were used according to the manufacturers' instructions (standard test, PT([ST])) and compared to a modified test procedure (modified test, PT([MT])) using sample dilution and fibrinogen addition. In all samples, sensitivity was lower (P<0.01) when using PT([ST]) with reagent 2 (0.20) than when using either PT([ST]) with reagent 1 (0.65) or PT([MT]) with both reagents (reagent 1, 0.60-0.75, reagent 2, 0.58-0.70, depending on sample dilution). The highest sensitivity was found for PT([MT]) when using a 1:20 sample dilution. In those samples in which at least one coagulation factor activity was decreased (by 20%; n=18), the sensitivity of PT([ST]) with reagent 2 (0.33) was found to be inadequate, in contrast to all other test procedures (0.83-0.94). This low sensitivity corresponded to shorter time intervals between different coagulation activity levels prepared by EPP dilution. The results indicate that adequate sensitivity of PT measurements in equine plasma can be achieved using a standard test procedure as long as a suitable reagent is used.
Mischke
R
R
Small Animal Clinic, Hannover School of Veterinary Medicine, Bischofsholer Damm 15, D-30173 Hannover, Germany. reihard.mischke@tiho-hannover.de
Junker
J
J
Deegen
E
E
D000818:Animals; D020147:Coagulation Protein Disorders / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D006734:Horse Diseases / Q000097:blood / Q000175:diagnosis*; D006736:Horses; D011516:Prothrombin / Q000032:analysis; D011517:Prothrombin Time / Q000379:methods / Q000592:standards / Q000662:veterinary*; D011933:Reagent Kits, Diagnostic / Q000592:standards / Q000662:veterinary*; D012680:Sensitivity and Specificity; D013918:Thrombin Time / Q000662:veterinary
D011933:Reagent Kits, Diagnostic; D011516:Prothrombin