Association Between Platelet Indices and Platelet Count in Patients with Immune Thrombocytopenia During Routine Follow-up

AimsTo evaluate the association between platelet indices and platelet count severity in patients with primary immune thrombocytopenia during routine post-treatment follow-up. MethodsThis retrospective observational study included patients with primary immune thrombocytopenia followed at a single tertiary care center between 2011 and 2025. Demographic and laboratory data were obtained from medical records. Platelet count severity was categorized as less than 30 x 10^9/L, 30 to 100 x 10^9/L, and greater than 100 x 10^9/L. Platelet indices, including mean platelet volume (MPV) and platelet distribution width (PDW), were analyzed using the most recent complete blood count obtained during routine follow-up after treatment initiation. Continuous variables were summarized as median and interquartile range. Comparisons across platelet count categories were performed using the Kruskal-Wallis test with post hoc Mann-Whitney U testing. Correlation analysis and simple linear regression were also conducted. ResultsA total of 243 patients were identified, of whom 232 met the inclusion criteria. Platelet distribution width differed significantly across platelet count severity categories (Kruskal-Wallis p < 0.001) and demonstrated a strong inverse association with platelet count. Mean platelet volume also showed a statistically significant difference across platelet count groups (Kruskal-Wallis p = 0.007), although the association was weaker and less consistent compared with PDW. Regression analysis confirmed a significant association between platelet count and PDW. ConclusionPlatelet distribution width is more closely associated with platelet count severity than mean platelet volume in patients with primary immune thrombocytopenia during routine post-treatment follow-up. PDW may represent a useful adjunctive laboratory parameter when interpreted alongside platelet count in routine clinical practice.