Outcome selection and reporting transparency in ClinicalTrials.gov-registered chronic spontaneous urticaria trials: a registry–publication linkage study

Background Chronic spontaneous urticaria/chronic idiopathic urticaria (CSU/CIU) trials increasingly evaluate biologics and targeted mast-cell therapies. Whether ClinicalTrials.gov-registered trials consistently capture patient-centred outcomes and disseminate results in a timely and linkable manner remains uncertain. Objectives To map registered outcome domains, patient-centred outcome breadth and reporting transparency among interventional CSU/CIU trials in ClinicalTrials.gov. Methods ClinicalTrials.gov was searched using three CSU/CIU-related queries, yielding 486 records and 168 unique NCT registrations after deduplication. Eligible interventional trials were coded for intervention category, trial purpose and nine registered outcome domains. A descriptive 0–8 patient-centred outcome score excluded safety. A stratified sample was independently recoded by a second author. Completed or terminated trials underwent manual registry–publication linkage, with primary and secondary publications distinguished and reporting assessed at 12, 24 and 36 months after primary completion using a fixed data lock of 1 June 2026. Results We included 128 eligible trials; 83 were completed or terminated. Disease activity/UAS7 (78.1%), itch/pruritus (65.6%) and wheals/hives (59.4%) were commonly registered, whereas urticaria control/UCT (28.1%), angioedema (30.5%), relapse/remission/rescue medication (24.2%) and explicit sleep/daily activity (7.8%) were less frequent. The mean patient-centred score was 3.37 (SD 1.98), and 20 trials (15.6%) scored at least 6. Independent second coding showed 90.4% agreement across 270 domain-level decisions. Among 83 completed/terminated trials, 32 (38.6%) had both posted results and a confirmed primary publication, whereas 15 (18.1%) had no qualifying public result identified. Any qualifying public result was available within 12, 24 and 36 months for 18.8%, 53.5% and 66.7% of trials with sufficient follow-up, respectively. Conclusions ClinicalTrials.gov-registered CSU/CIU trials show substantial heterogeneity in patient-centred outcome coverage. Distinguishing trial purpose, primary from secondary publications and reporting opportunity over time provides a more cautious assessment of the registered evidence base and highlights opportunities for more harmonised outcome selection and clearer result dissemination.