Abstract: Objective　To establish the healthy subjects′ immature platelet fraction (IPF) parameter reference range in Tianjin，and to investigate its significance in the diagnosis of thrombocytopenic disease.  Methods　By XE-5000 automatic hematology analyzer，2 600 healthy subjects′ peripheral blood absolute value of immature platelet fraction [IPF(#)]，the percentage of immature platelet fraction [IPF(%)]，the percentage of high fluorescence immature platelet fraction[H-IPF(%)] and platelet(PLT) in Tianjin were detected. These parameters in 23 patients with idiopathic thrombocytopenic purpura (ITP)，29 patients with acute aplastic anemia (AA)，10 patients with acute promyelocytic leukemia ( AML-M3 )  and 24 patients with AA treated with anti-thymocyte globulin remission after treatment ( AA-CR ) were detected. The differences between disease group with various diseases and the healthy control group were compared，and the parameter diagnosis significances in various diseases were analyzed.  Results　For healthy control group，the 95% reference ranges were IPF (#)： 0.7-5.6×109/L，IPF (%)： 0.3%-2.8%，H-IPF(%)：0.0%-0.8% and PLT:143-333×109/L. The above parameters except PLT had statistical significance between males and females (P<0.05 ). In ITP group and AML-M3 group，IPF(#)，IPF(%)，H-IPF(%) and PLT had statistical significance compared with healthy control group (P<0.05 ). In AA group，IPF(#)，IPF(%) and PLT had statistical significance compared with healthy control group(P<0.05 ). In AA-CR group，IPF(#) and PLT had statistical significance compared with healthy control group(P<0.05 ). The sensitivity of IPF(%) in ITP group was 90.0%，the specificity was 95.7% and the largest Youden index was 85.7%. The sensitivity of IPF (#) in AA group was 90.0%，the specificity was 100%，and the largest Youden index was 90%. The sensitivities of H-IPF (%) in ITP group and AML-M3 group were 98.3% and 82.5%，the specificities were 69.7% and 90.0%，and the largest Youden indices were 77.9% and 72.5%.  Conclusions　The reference ranges of IPF(#)，IPF (%) and H-IPF (%) among healthy subjects in Tianjin are established，and the different PLT parameters in different thrombocytopenia disease have certain clinical significance.

Key words: Immature platelet fraction, Platelet, Thrombocytopenic disease, Automatic hematology analyzer