Is bone marrow aspiration needed in acute childhood idiopathic thrombocytopenic purpura to rule out leukemia?

OBJECTIVE To assess the prevalence of leukemia in a series of bone marrow aspiration (BMA) samples collected to confirm provisional diagnoses of acute idiopathic thrombocytopenic purpura (ITP) in children. DESIGN A retrospective cohort. SETTING All BMA reports at The Hospital for Sick Children, Toronto, Ontario (a tertiary care pediatric hospital), from January 1, 1984, to May 31, 1996, were reviewed. PATIENTS Included were BMAs performed to confirm provisional diagnoses of ITP in children (6 months to 18 years of age) with "typical" contemporaneous hematologic features of ITP (platelet count, < or =50 x 10(9)/L; hemoglobin level, > or =100 g/L [6-12 months of age] or > or =110 g/L [> 1 year of age]; white blood cell count, > or =5 x 10(9)/L [6 months to 6 years of age] or > or =4 x 10(9)/L [> 6 years of age]; and neutrophil count, > or =1.5 x 10(9)/L [6 months to 6 years of age] or > or =2 x 10(9)/L [> 6 years of age]). Children with chronic ITP, thrombocytopenia-related chronic conditions, or leukemic blasts on peripheral smears were excluded. MAIN OUTCOME MEASURE The finding of leukemia in the BMA report was chosen a priori as the primary outcome for the yield of BMA. RESULTS Four hundred eighty-four BMAs were performed to confirm provisional diagnoses of acute childhood ITP. No diagnoses of leukemia were revealed in the 332 children with typical hematologic features of ITP. The risk of missing the diagnosis of leukemia in this setting is less than 1%. CONCLUSIONS The yield of BMA for leukemia in this setting is low. Routine BMA is not necessary for children with typical acute ITP.