Assessing uptake of the core outcome set in clinical trials for immune thrombocytopenia: A cross-sectional analysis

Introduction: Clinical trials (CTs) guide clinical practice, but inconsistent outcome reporting presents challenges. To increase comparability, a core outcome set (COS) was created for primary Immune thrombocytopenia (ITP) in 2009 to standardize outcome measurements. We aimed to evaluate uptake of the primary ITP COS in CT registries. Materials & methods: Our cross-sectional analysis employed a search string on ClinicalTrials.gov and ICTRP for phase III/IV CTs in June 2023. Inclusion criteria consisted of subjects with primary ITP, study was registered five years before COS publication to June 26, 2023, and assessed effectiveness of interventions. Two investigators extracted data in a masked, duplicate manner. Interrupted time series analysis, ANOVAs, and correlation analyses were conducted to assess the main outcome of COS uptake pre/post COS publication. Results: The search identified 131 eligible trials for data extraction. Altogether, 38.2 % (50/131) followed IWG platelet response guidelines. An alternative platelet count measurement was 50,000 × 10⁹ L, with 46.56 % (61/131) of trials reporting it. The most measured outcome was adverse events (106/131, 80.9 %). Remaining secondary outcomes were measured in <50 % of studies. After COS publication, there was a statistically non-significant 0.03 % (p = 0.50, CI 95 % = [−0.06, 0.13]) 0.03 % (p = 0.50, CI 95 % = [−0.06, 0.13]) increase in the monthly trend of COS-defined outcomes. Conclusion: We found a non-significant increase in uptake of the ITP COS since its publication and highlighted the lack of standardization among endpoints within ITP clinical trials. Our analysis highlights the need for heightened awareness and a COS update that acknowledges the variability in clinical trials.