| Abstrakt: |
A multivariate analysis of results of 512 individuals, (more than half less than 20 years of age) referred to the University of Manitoba Coagulation Laboratory, was performed to assess the relationship of age, sex, and various coagulation parameters to the length of the bleeding time (BT). Patient age (children had longer BTs than adults, even with other factors normal), platelet aggregation to collagen and epinephrine, platelet adhesion (ADH) and prothrombin consumption (PC) emerged as important and independent variables (p<0.01). Controlling for other variables, including von Willebrand (vW) Ag and ristocetin cofactor (RC), did not change the correlation of ADH and BT, but decreased that between PC and BT. Where vWAg, vWRC and factor VIII were all less than 120%, there was a weak negative correlation between the length of the BT and vWAg or vWRC. In contrast, where any one of these three parameters was 120% or greater, there was a weak positive correlation between vWAg or vWRC and the BT. However, the mean BT of all (8) patients with vWAg or vWRC less than 55%, normal aggregation and PC greater than 80%, was in the normal range (7.56 min). The view that vWAg level, or activity as assessed by vWRC, is, by itself, a major determinant of the length of the BT should be revised. Platelet adhesion, independent of factor level (vWAg) or activity (vWRC) appears more important. |
