BACKGROUND: Immune thrombocytopenia (IT) is one significant cause of severe thrombocytopenia in pediatric patients. Classic presentation of IT is bleeding, thrombocyte count <100.000/mm3, and preceeding viral infection before the onset of IT. Bone marrow aspiration (BMA) still perform due to fear of misdiagnosis with acute leukemia or aplastic anemia. The immature platelet fraction (IPF) will increase in IT due to peripheral destruction of immune mechanism. 
OBJECTIVE: To find out the diagnostic value of the IPF compared to bone marrow aspiration in pediatric immune thrombocytopenic purpura (IT) diagnosis.
METHOD: This cross sectional study conducted from pediatric hematology register book and then confirmed with patient’s medical record aged 1–18 years with thrombocytopenia on January 2015–May 2019 in Hasan Sadikin Hospital, Bandung. Samples recruited as research subject was 51 patients who fulfilled inclusion criteria that is complete medical record, thrombocytopenia patient with clinically and laboratory as IT who was conducted bone marrow aspiration and blood examination consist of complete blood count, IPF, and peripheral blood smear. Exclusion criteria are thrombocytopenia patient who is clinically obvious not as IT, such as critically ill patient, sepsis, or other autoimmune diseases. Statistical analysis used diagnostic test in the form 2x2 tables.
RESULT: Fifty one patients met inclusion criteria, 34 with ITP, 13 with bone marrow failure (BMF), and 4 with  malignancy. BMF such as amegakaryocyte thrombocytopenia, myelodysplasia syndrome, aplastic anemia, and malignancy such as acute leukemia confirmed by BMA result. An elevated IPF differentiated IT from BMF with 82% sensitivity and 82% specificity. In this study, likelihood ratio negative is 0,12, positive predictive value is 90%, and negative predictive value is 70%. Accuracy for this test also 82%. The AUC value for IPF is 0.86 with CI 95% (0.74-0.97).
CONCLUSION: Elevated IPF provides useful supportive tools for the diagnosis of IT. Further study is required to confirm this finding with optimum sample size.