The species specificity of thromboplastin (tissue factor) is an important fact to take into consideration when clotting assays or experiments are planned. We have (re)investigated all possible combinations of thromboplastin and plasma from several of the most commonly used species of experimental animals.
The Activated Partial Thromboplastin Time (APTT) test, Cephotest, was compared to other APTT methods in current use in 4 specialized coagulation laboratories. In 3 of 4 laboratories, the sensitivity of Cephotest was superior (P < 0.001) to that of the local APTT method. There was no statistically significant difference between the APTT methods with regard to precision of repetitive testing.
In each laboratory, the normal range of Cephotest was estimated on freshly collected plasma samples from healthy subjects. A mean value between 28.8 and 35.8 s, with a standard deviation of 1.1–3.3 s, was obtained.
It is concluded that the composition of the APTT method is of importance for the sensitivity of this test, but does not influence the precision of repetitive testing to a significant degree. The use of a standardized reagent facilitates comparison of the results obtained with the APTT method from one laboratory to another.
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