Bullous Pemphigoid Outcome Measurement: A Scoping Review of Outcome Heterogeneity and Trends in Clinical Research of Treatments

Background Bullous pemphigoid (BP) is the most common autoimmune bullous disease, characterized by development of tense blisters and pruritus. BP is a chronic disease, requiring long-term treatment often associated with serious side effects. Developments in understanding the disease have led to novel treatment approaches evaluated in clinical trials, however pooling of trial data remains challenging due to inconsistent outcome reporting. Objective This scoping review aims to provide an overview of BP outcome measurement of two decades by mapping and listing all previously reported treatment outcomes and outcome measurement instruments (OMIs). Methods A large scoping review was performed in scientific databases and trial registries covering January 2002 to August 2025. Study selection and data extraction were performed by a minimum of two reviewers independently. Eligible study designs were clinical trials, prospective cohort studies and systematic reviews. Retrospective studies were excluded. All identified outcomes and OMIs were mapped into overarching domains for insights into outcome measurement trends over time, including the uptake of consensus definitions. Results Eighty studies were included, consisting of clinical trials (n=27), prospective cohort studies (n=27), and systematic reviews (n=26). A total of 659 outcomes were extracted verbatim and classified into 46 outcome domains across 10 outcome domain areas. Clinical response, safety and immunological response comprised a major part of outcome measurement. Moreover, steroid toxicity was increasingly considered in clinical trials. Definitions and timepoints of clinical response varied considerably. An imbalance between patient-reported and clinician-reported outcomes was revealed, with patient-reported outcomes being in the minority, as well as a diverging focus between primary analyses in clinical trials and secondary analyses in systematic reviews. OMIs used for measuring patient impact and quality of life were mainly generic and only sparsely used. Conclusions Over the past two decades, BP research has shown considerable heterogeneity in reported outcomes and OMIs. Despite standardization efforts, most studies lack well-defined, consistent outcomes. Redefinition of some endpoints and a consensus-based approach towards outcome uniformity should bridge regulatory requirements with validated sensitive measurement and patient-related outcomes. This approach would enhance the clinical relevance of trial endpoints while maintaining standardization, ultimately advancing both research quality and therapeutic development.