Clinical diagnosis of chronic immune thrombocytopenic purpura in pediatric population - is it always correct?

1717 Objectives To investigate patophysiological mechanism of thrombocytopenia with 111In-oxinate labeled autologous platelets in children with clinical diagnosis of chronic immune thrombocytopenic purpura (ITP), to verify the diagnosis, and to predict the efficacy of the planned splenectomy. Methods 69 children (44 girls/25 boys) aged from 3,1-18,0 yrs (median=11 yrs), body height: 100-187cm (mean=147cm), body weight:15-98kg (median=34kg) were investigated. 69 autologous Pt 111In-oxinate labelings; quality control: a) general and differential yields of Pt labeling, b) initial platelet accumulation in the liver (IPAL); Pt lifespan (LS); production index (PI); sequestration site and index estimation were performed. Results Median Pt blood count was 21 G/l (1-122 G/l). Blood sample volume taken for Pt separation was 30-75ml (mean=55ml). Radioactivity used for Pt labeling was 11.1 MBq. Mean injected radioactivity was 6.7 MBq (2.6-10.1 MBq), depending on Pt blood count. Mean general yield of labeling was 65.9 % (33.9-90.2 %). Mean differential yield of Pt labelling was 92.6% (55.7-99.6%), of RBCW 4 children had inadequate Pt PI which ranged from 0.1-0.2). In 63/69 children diagnosis of ITP was confirmed. In this group Pt LS range was 0.7-93.6h (median 9.6h), Pt PI was 0.2-23.4 (median=1.8), sequestration index 0.3-9.4 (median=1.8). Sequestration site was the spleen in 26 (42%), predominantly spleen in 9 (14%), liver in 3 (5%), mixed (in liver and spleen equally) in 24 (39%). Conclusions In 6/69 children initial diagnosis of ITP was changed: 2/69 pseudothrombocytopenias, 4/69 inadequate platelet production. In 63/69 children ITP was confirmed. Help in decision whether to perform splenectomy or not was enabled in 61.3%.