The association between immature platelet count and clinical characteristics in pediatric immune thrombocytopenia

Despite the increasing number of treatments for immune thrombocytopenia (ITP), there are no established laboratory predictors of treatment response. Immature platelet fraction (IPF) and immature platelet count (IPC) are clinical laboratory measurements reflecting bone marrow thrombopoietic activity. The association between IPF and IPC and response to treatments, including thrombopoietin receptor agonists, has not been previously studied in children.

This study evaluated the relationship among IPF, IPC, and treatment response in children with ITP.

This observational cohort study included 4 pediatric medical centers. Inclusion criteria were a diagnosis of ITP, ITP medication treatment, and an available clinical IPF measurement. Laboratory and clinical data were collected via medical record review.

A total of 195 patients were included, with a median age at diagnosis of 7.5 years (range, 0.1-20.7). IPF was inversely associated with platelet count, whereas IPC was positively associated with platelet count. IPC at diagnosis and pretreatment was higher in overall responders than in nonresponders (P = .03 and P = .001, respectively). There were higher pretreatment platelet counts in overall responders than in nonresponders (P < .001), but no differences in IPF at diagnosis or pretreatment between the treatment groups. Pretreatment IPC and platelet count were higher in corticosteroid responders than in nonresponders (P = .046 and P = .005, respectively), and in intravenous immunoglobulin responders than in nonresponders (P = .04 and P = .003, respectively). However, pretreatment IPF, IPC, and platelet counts did not differ between thrombopoietin receptor agonist responders and nonresponders.

Higher pretreatment platelet count and IPC correlate with overall treatment response, but the association varies by individual treatment. Biomarkers of treatment response are needed to inform individualized management.