Immature platelet count: a simple parameter for distinguishing thrombocytopenia in pediatric acute lymphocytic leukemia from immune thrombocytopenia.

BACKGROUND: Platelet counts below normal values define thrombocytopenia. However, platelet counts alone do not reveal the underlying pathomechanism. New blood cell counters provide additional information on platelet size and volume, and enable the distinction of sub-populations. In this preliminary study, we evaluate whether one of these markers can be used for diagnosis of isolated thrombocytopenia in children.

PROCEDURE: We provide normal values for mean platelet volume (MPV), platelet distribution width (PDW), plateletcrit (PCT), platelet large cell ratio (P-LCR), platelet mean-frequent volume (P-MFV), relative immature platelet fraction (IPF%), and absolute IPF (IPF#) for 100 healthy children and analyzed 87 children with thrombocytopenia.

RESULTS: In children with platelet production defects, IPF% was low, while in acute immune thrombocytopenia (ITP), IPF% was markedly increased (median 25.2%, P < 0.01), representing accelerated platelet turnover. Interestingly, children diagnosed with acute lymphocytic leukemia (ALL) also had elevated IPF% (median 10%, P < 0.01), suggesting that thrombopoiesis is stimulated despite virtual absence of bone marrow progenitors. Low IPF# was only found in patients with acute ITP.

CONCLUSIONS: IPF% is a marker for thrombocytopenia due to defective platelet production while IPF#, representing the immature platelet count, might become a practical parameter to distinguish acute ITP from thrombocytopenia in children with newly diagnosed ALL (P < 0.01).