Platelet survival determined with51Cr Versus111In

Optimal labelling conditions of human platelets with111In-oxine were determined in vitro. Based on this optimized technique, platelet mean life span (MLS) and platelet sequestration site were comparatively evaluated in 79 patients with two labels,51Cr (n=26) and111In (n=53). Patients were subgrouped according to clinical criteria as autoimmune thrombocytopenic purpura (AITP) (group 1;n=49), hypersplenism (2;n=12), impaired thrombopoiesis (3;n=3), unclassified thrombocytopenia (4;n=6), and nonthrombocytopenic patients (5;n=9). In patients with AITP and hypersplenism the mean values for the MLS determined either with51Cr or with111In were lowered but the difference was not statistically significant, neither for group 1 (18.6 h vs 17.3 h;P>0.2) nor for group 2 (94.7 vs 122.3 h;P>0.2). The correlation between MLS and platelet counts in patients with AITP was significant for both labels (P<0.001). The 15 min recovery tended to be higher with111In in all groups, but the difference was significant (P<0.05) only for group 1. The sequestration sites were similar with both labels. We conclude that, contrary to previous reports, platelet survival studies yield similar results with both the51Cr and111In methods. Due to its distinct advantages111In is the label of choice for investigation of platelet kinetics.