Cord blood platelet aggregation; quality control by a two-sample technique

Two blood samples were taken from the cords at 17 normal deliveries 2-4 min and 5-8 min after birth, respectively. The difference in platelet count between early and late samples in platelet-rich plasma was less than 5% in nine cords (Group A), and greater in eight cords (Group B). Platelet aggregation studies on the early and the late blood samples showed consistent results within each cord in Group A but not in Group B. The correlations between the responses were high for Group A. The aggregation responses were also slightly but significantly higher in the late samples in this group (p less than 0.01 in Group A; n.s. in Group B). The differences between responses in early and late blood samples could not be explained by acid-base dissimilarities. The variability in cord blood platelet aggregation results can be greatly reduced by platelet counting in PRP of two independent blood samples, accepting only samples with concordant platelet counts (less than 5% difference).