Clinical relevance of immature platelet fraction in thrombocytopenia and its role in differentiating bone marrow suppression and destruction of platelets

Thrombocytopenia is a condition with low platelet counts resulting from decrease in bone marrow production of platelets or increase in platelet destruction. The reticulated platelets were discovered in 1969 and many research studies gave evidence of it being sensitive marker of thrombopoiesis. Earlier it was estimated by fluorescence flow cytometry but since 1990’s a new method is introduced to estimate reticulated platelets and is termed as automated method. Various platelet parameters obtained by automated hematology analyzer are Mean platelet volume, plateletcrit, platelet distribution width, platelet large cell ratio and immature platelet fraction. Immature platelet fraction is one of the component of automated method used to assess the thrombopoietic activity in bone marrow. Rinder et al. showed that an increased percentage of reticulated platelets indicated in thrombocytopenia correlated well with increased megakaryocytic proliferation in bone marrow whereas decrease in percentage of reticulated platelets indicated decrease in number of bone marrow megakaryocytes. Zeigler et al. reported that large platelets were seen in individuals with thrombocytopenia due to Immune thrombocytopenic purpura whereas platelet size was normal in patients with thrombocytopenia due to bone marrow aphasia, hypersplenism and thrombotic thrombocytopenic purpura with a normal platelet count. Briggs et al. in 2004 published a study done on SYSMEX XE stated, increase in immature platelet fraction was seen in individuals with immune thrombocytopenic purpura (mean 22.3%; range 9.2-33.1%) and thrombotic thrombocytopenic purpura (mean 17.2%; range 11.2-30.9%). The normal range was taken as 1.1-8.1%. They also noted that as the platelet count increases the immature platelet fraction percentage falls. Abe et al. showed that the immature platelet fraction was significantly higher in patients with immune thrombocytopenic purpura and significantly lower in patients during the nadir phase post chemotherapy and in normal range in incomplete immune thrombocytopenic purpura patients and those with aplastic anemia. Linden et al. showed that immature platelet fraction could be used as a predictor of platelet recovery within 2 days using cut-off of 5.3% in patients receiving autologous stem cell transplantation.