The capillary thrombometer revisited.

A modified capillary thrombometer was constructed to study the rate of thrombus formation using heparinized whole blood (2 U/ml) obtained from normal adults (n = 22) and children (n = 20) and patients with hemophilia A (n = 10) or von Willebrand's disease (n = 8). The median thrombosis times were as follows: normal adults = 12.8 min (range = 4.5-26.0), normal children = 13.3 min (range = 5.7-29.0), patients with hemophilia A = 37.2 min (range = 20.0-60.0 min), and patients with von Willebrand's disease = 60.0 min (range = 37.2-60.0). Significant differences were demonstrated between all groups of subjects, except between normal adults and children. The capillary thrombometer appears to measure thrombus formation dependent on adequate Willebrand factor and platelets.