Platelet function tests in childhood. Measuring aggregation and release reaction in whole blood

Blood samples from 42 newborns, 78 infants and schoolchildren, and 81 healt hy adults were tested for the parameters of primary hemostasis. Only whole blood techniques were used. Agonist-induced aggregation and release-reactio n studies were performed in a whole blood lumi-aggregometer simultaneously. The release of adenosine triphosphate (ATP) was detected by the luciferin- luciferase method. The in vitro bleeding time was measured by the PFA 100(R ) system. The results of these studies were ostensibly influenced by blood cells. Many aggregation phenomena were correlated with the platelet count. Aggregation and release reaction by collagen were inversely correlated with the hematocrit. In the PFA 100(R), hematocrit and leukocyte count were als o inversely correlated with the closure time and the maximal blood flow vel ocity. Both parameters were diminished in newborns. The aggregation respons e to adenosine diphosphate (ADP) was similar in the three groups. The same was true for the aggregation and release reaction by arachidonic acid and f or the agglutination by ristocetin, The aggregation and release reaction by collagen were diminished in the specimens from newborns. For the explanati on of this transient hypofunction, only theoretical considerations exist. B eyond the postnatal period and during childhood, no remarkable differences from the adult norm were found.