[A modified in vivo platelet retention test in the evaluation of primary hemostasis].

A simple assay system for measuring platelet retention in a standardized superficial skin wound is presented. Platelets were counted in the blood collected at the site of the wound 1, 2 and 3 minutes following incision. Per cent platelet retention was calculated from the difference between venous blood platelet count and wound blood platelet count, divided by venous count. The time course of platelet retention, measured in 20 healthy persons, reflected the sequence of primary and secondary platelet aggregation. Ten patients with congenital platelet defects already showed impaired platelet retention in the early stage of bleeding. On the other hand, administration of aspirin to 10 healthy subjects inhibited only the late stage of platelet retention. In comparison with the template bleeding time our platelet retention test provides additional information useful for evaluating congenital and drug-induced defects in platelet plug formation.