Serial studies in von Willebrand's disease: variability versus "variants".

The variability of laboratory findings in von Willebrand's disease (vWd) was evaluated by performing serial studies of bleeding time (BT), factor VIII coagulant activity (VIII:C), factor-VIII-related antigen (VIIIR:Ag) and ristocetin cofactor (VIIIR:Rcof) in 50 individuals from 25 families with this disorder. The types of results were characterized from 1 to 16 based on the possible combinations of findings using these four tests. The only patients observed to have consistently abnormal results of all four tests were three individuals with homozygous vWd.

Ontogeny of bovine hemostasis.

Ontogeny of selected hemostatic system components was studied in 120 bovine fetuses which had been divided into eight monthly gestational age groups. Fetal blood was subjected to the following tests: platelet count, partial thromboplastin time, prothrombin time, thrombin time, fibrinogen quantitation, and assays for prothrombin and factors V and VIII. Platelet numbers corresponding to adult numbers were in fetal blood at least as early as gestation day 60, and their numbers varied only slightly thereafter.