title: Evaluation of a prothrombin time optimized for the dog on plasmas with defined coagulation factor deficiency due to coumarin intoxication.
abstract: The sensitivity of the standard prothrombin time (PT) was low when measured on 56 plasmas with a reduced activity of the coagulation factors mainly of the prothrombin complex (factors II, VII and/or X) taken from eight dogs at different times of vitamin K1 therapy after coumarin intoxication. This was demonstrable by use of three different Ca-thromboplastins. With the standard test only plasmas with an excessive decrease of coagulation factor activity (sum of activity decrease of the single factors in relation to the respective reference range [SAD] > 100%) were detectable with sufficient reliability. In contrast, by using a method optimized for dogs (1:20 sample predilution, fibrinogen substitution) and respecting the species specific features of coagulation physiology, pathological PT-values were measured in up to 70% of the samples (dependent on the Ca-thromboplastin) with slight reductions of single factor activity (SAD: 11-25%). Significant differences concerning the sensitivity were seen additionally between the different Ca-thromboplastins. Human placenta thromboplastin in particular, but also rabbit brain thromboplastin, were more sensitive than a preparation of recombinant human tissue factor. The correlation between the PT and the SAD was closer when using the optimized method (r = 0.919-0.954) compared to the standard test (r = 0.771-0.862). In contrast to the standard test, the PT optimized for dogs is, therefore, a reliable screening test to recognize a slight reduction in prothrombin complex. It is especially suitable for monitoring of vitamin K1 therapy after coumarin intoxication.
authors.affiliation: Clinic of Small Animals, Hanover School of Veterinary Medicine, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Mischke
mesh_terms: D000818:Animals; D001778:Blood Coagulation Disorders / Q000097:blood / Q000139:chemically induced / Q000662:veterinary*; D003374:Coumarins / Q000506:poisoning*; D004283:Dog Diseases / Q000097:blood* / Q000139:chemically induced; D004285:Dogs; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D011517:Prothrombin Time / Q000662:veterinary*; D012016:Reference Values; D012680:Sensitivity and Specificity; D014812:Vitamin K / Q000627:therapeutic use
chemical_list: D003374:Coumarins; D014812:Vitamin K; C030123:coumarin