CO095 | IMMATURE PLATELET FRACTION PREDICTS CLINICAL INSTABILITY IN CHRONIC IMMUNE THROMBOCYTOPENIA: PRELIMINARY RESULTS FROM THE PLATE-RET STUDY

F. Boggio^1|2, J.A. Giannotta¹, M. Abbattista¹, M. Clerici¹, S. La Marca¹, L. Padovan^1|2, A. Truma¹, A.C. Migliorini³, S. Torricelli³, A. Lecchi^1|2, A. Artoni¹ | ¹Centro Emofilia e Trombosi A. Bianchi Bonomi, IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico di Milano, Italy; ²Dip. di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Italy; ³Settore di Ematologia, Lab. Analisi, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, Italy

Background. Effective management of Immune Thrombocytopenia (ITP) is hindered by the lack of biomarkers reflecting disease activity and predicting clinical course. The utility of indexes of platelet turnover and thrombopoietic drive, such as immature platelet fraction (IPF) and thrombopoietin (TPO), in adult ITP remains undefined.
Aims. To evaluate IPF and TPO in adult ITP patients compared to healthy controls (HC) and their predictive value for 6 months outcomes.
Methods. The PLATE-RET study is an ongoing monocentric observational study enrolling adult ITP patients and matched HC. IPF% was measured via a Sysmex XN-9000 analyzer. Serum TPO was measured by ELISA. A subset of persistent/chronic patients were followed for 6 months. A Composite Adverse Outcome (CAO) was defined as active bleeding (WHO>0), platelet count drop >40%, and rescue therapy/dose escalation. Statistics included the Mann-Whitney U-test and logistic regression. Informed consent was obtained; the study was approved by the local Ethics Committee.
Results. We enrolled 80 ITP patients (median age 56 years; females 58.8%) and 29 HC. Patients exhibited higher IPF% (11.3% vs 7.0%, p<0.001) and TPO (84.0 pg/mL vs 63.9 pg/mL; p=0.001) than HC. Stratification revealed that IPF levels were significantly higher in patients with platelet count <50x10⁹/L compared to >50x10⁹/L (20.7% vs 9.15%; p<.001), while TPO was higher in patients in therapy (94.3 pg/mL vs 60.5 pg/mL; p=0.002) (Figure, Panels A and B). In the longitudinal cohort of persistent/chronic patients (n=46), 56.5% experienced the CAO. In univariate logistic regression, higher baseline IPF% significantly predicted the occurrence of CAO (OR 1.11 per unit increase, 95% CI 1.03–1.19). In multivariate analysis, high IPF remained an independent predictor of instability in patients on active therapy after adjusting for platelet count (Figure, Panel C), whereas TPO levels showed no prognostic value (p=0.355).
Conclusions. Adult ITP is characterized by significantly higher IPF and moderately higher TPO levels compared to HC. High baseline IPF predicts clinical instability at 6 months in patients on therapy, whereas TPO lacks prognostic value. This identifies a high-risk subgroup where elevated IPF may warrant closer monitoring.