Kinetics and distribution in vivo of 111In‐labelled autologous platelets in idiopathic thrombocytopenic purpura

Abstract

The kinetics of autologous ¹¹¹In-labelled platelets were studied in 26 patients with ITP. The platelet mean life time (MLT) was considerably shortened, the platelet in vivo recovery slightly lowered and the platelet turnover normal. Comparative studies of the kinetics of simultaneously injected ¹¹¹In- and ⁵¹Cr-labelled platelets in 10 patients showed the MLT and turnover of ⁵¹Cr-platelets to be shorter and higher, respectively, than those of ¹¹¹In-platelets, suggesting that ⁵¹Cr-labelling in ITP may underestimate platelet MLT and overestimate platelet turnover. Our results confirm that accelerated platelet destruction is an important pathogenetic factor in ITP, and that the platelet concentration may be influenced by increased splenic platelet pooling and by inability of the bone marrow to respond adequately to the low platelet count. Our scintigraphic studies showed that the spleen played an important role for platelet destruction in most patients, with the liver contributing in some patients.