Age at Diagnosis Shapes the Prognosis of Childhood Immune Thrombocytopenia

Abstract

Objective: Childhood immune thrombocytopenia (ITP), an acquired bleeding disorder, occurs at any age. Studies have indicated a less favorable prognosis in children aged above ten years. Low lymphocyte counts have been proposed as predictors of chronic disease. Detailed knowledge of ITP disease characteristics and prognosis at various ages may be useful to support clinical decision-making. We aimed to define the age dependency of the clinical characteristics, biological parameters and disease outcomes in childhood ITP. Design: Post-hoc analysis of two prospective European studies (NOPHO ITP study and TIKI trial). Children were followed for 6-12 months. Setting: Patient inclusion in pediatrics departments in the Netherlands and the five Nordic countries. Patients: Children aged <16 years with newly diagnosed ITP (N=577) and severe thrombocytopenia (diagnosis platelet count ≤20 x 109/L). Results: By analyzing age effects on a continuous scale, we observed that recovery rates at 3-12 months follow-up were gradually reduced in children aged above five years. An absence of a response to IVIg was observed at all ages, but was more common in older children, in particular above ten years of age. Leukocyte and lymphocyte subset counts were reduced with age, but not elevated or decreased compared to age-appropriate reference intervals. Children aged below seven years showed elevated thrombopoietin levels. Conclusions: Already from five years of age onwards, there is an increasing risk for a long-lasting course of ITP. Given the varying treatment responses and biological variation, age differences should be considered for the design of clinical trials, prediction models and biological studies.