Failure of Routine Coagulation Screening Tests to Detect Heterozygous State of Bovine Factor XI Deficiency.

In a survey of coagulation, biochemical and hematological parameters in cattle homozygous (deficient), heterozygous (carrier) and non-affected (normal) for Factor XI deficiency, only the Activated Partial Thromboplastin Time (APTT) results correlated with plasma Factor XI activity levels. The APTT results and the thrombokinetics for the deficient animals were markedly different from the results of either the carrier or normal animals. However, the APTT assay was shown not to be sufficiently sensitive to differentiate between the normal and carrier state for the coagulation disorder. Not only was there no statistical difference between the mean APTT results for the normal and carrier animals, but the thrombokinetics for fibrin clot formation for the two groups were also similar.