Abstract
Introduction
Reticulated platelets (RP) were suggested that those cells might contain increased amounts of cytoplasmic RNA, reflecting the rate of thrombopoiesis in bone marrow. The flow cytometric analysis has been used for RP assay, however it was difficult applying to routinely testing due to complicated operations. We developed a new automated RP testing method named as immature platelet fraction (IPF) using XE-2100 automated hematology analyzer equipped with modified software and a polymethine dye. The aim of the study is to evaluate the IPF as indicator to discriminate level of thrombopoiesis in thrombocytopenic patients.
Methods
We have analyzed IPF in 129 healthy volunteers (40 females and 89 males; range, 21–60 years), and in 127 consecutive, unselected patients in Mie University Hospital from June 1, 2002 to March 31 2003. IPF was measured in the patients categorized to three groups which are different level of thrombopoiesis phase as ‘suppressed’ (Chemotherapy-induced hypoplasia (n=80)), aplastic anemia (AA) (n=24)), ‘increased’(idiopathic thrombocytopenic purpura (ITP) (N=51), Thrombotic thrombocytopenic purpura (TTP) (n=9)), the peak value of IPF preceding with platelet recovery (peripheral blood stemcell transplant (N=5)), bone marrow transplant (N=1), chemotherapy (N=101)), liver transplant (N=2))), high of FDP (>10μL/mL) group (N=19)) and ‘normal’(healthy volunteers (N=129)). Peripheral blood was collected in EDTA anti-coagulant. Total platelet counts and IPF were determined by the XE-2100 (Sysmex). Analysis of IPF was performed by special designed software. A receiver operating characteristic (ROC) curve was plotted for choosing optimized cut off value of IPF to discriminate different level of thrombopoiesis.
Results
Mean IPF value in healthy volunteer was 3.3±1.7 (%). IPF in ‘increased’ group was significantly higher than ‘suppressed’ and ‘normal’ group (p<0.01). In ‘increase’ group, IPF was significantly elevated in ITP (especially active phase; 16.5±9.2 %), TTP (13.4±3.1 %) and the peak value of IPF prior platelet recovery (11.4±5.4 %). The best cutoff point of IPF was chosen to discriminate ‘increased’ group from ‘suppressed + normal’ group was 6.15 (%). The sensitivity and specificity of this cutoff value are 80.0% and 90.1% for distinguish ‘suppressed + normal’ group, 80.0% and 83.7 % for distinguish ‘suppressed’ group. The positive predictive value was 89.4%, and negative predictive value was 70.7% to detect the ‘increased’ group from ‘suppressed’ group.
Summary
Our results suggest that the IPF reflects the level of thrombopoiesis in thrombocytopenic disorders. This simple technique of IPF measurement is useful for the differential diagnosis and analysis of platelet kinetics in thrombocytopenic patients.
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