Matter RM, et al. - This study examined the frequency of thrombocytopenia in children with congenital cyanotic heart disease (CCHD) and determinants of platelet count including immature platelet fraction (IPF) and their role in the pathogenesis of thrombocytopenia. Findings suggested that peripheral platelets destruction might be an underlying mechanism, as indicated by elevated IPF in CCHD patients with thrombocytopenia. In addition, it was observed that hemoglobin level, red blood cells (RBCs) count, hematocrit (Hct), and reticulated hemoglobin content (RET-He) were not significant determinants for platelet count in CCHD.