Absolute lymphocyte counts as prognostic indicators for immune thrombocytopenia outcomes in children

Background: Recent studies reviewing immune mechanisms of immune thrombocytopenia (ITP) have suggested acute and chronic forms may represent distinct immunopathological disorders. This study evaluated absolute lymphocyte counts (ALCs) as predictors for ITP outcomes. Procedure: CBCs with differential counts were ascertained at presentation, 3, 6, and 12 months for 204 patients. Receiver operating characteristic (ROC) curves were used to determine cutoff values. Logistic regression models and recursive partitioning were used to evaluate which variables were significantly associated with outcomes. Results: ALC values at presentation were not independently predictive of disease duration. However, ALC values at 3 months were significant predictors. Sixty-eight percent (40/59) of patients >8 years of age and 43% (20/46) of patients ≤8 years who had an ALC≤3,000/μl at 3 months developed chronic ITP. This compares to chronic rates of only 25% (3/12) and 2% (2/87) of patients >8 and ≤8 years, respectively, with an ALC>3,000/μl at 3 months. Further, 92% (60/65) of patients who developed chronic ITP had a 3-month ALC≤3,000/μl. An ALC>3,000/μl at 3 months is a strong predictor for platelet recovery as only 5% (5/99) of these patients developed chronic ITP. Conclusion: This study suggests progression to lower lymphocyte counts over the first few months of disease is a strong predictor for chronic ITP, allowing for risk stratification of patients, particularly when used in conjunction with other known predictors. Further research is needed to confirm these findings and to fully investigate the pathophysiological mechanisms responsible for this association. Pediatr Blood Cancer 2013;60:1967-1974.