Addressing cohort reliance in rare diseases literature: a scoping review of myositis research.

Abstract

This scoping review aimed to evaluate the extent and impact of duplication bias within contemporary idiopathic inflammatory myopathy (IIM) research. A systematic scoping review was conducted to identify original research articles on IIM published between 1 January 2021 and 18 May 2023 using MEDLINE and EMBASE databases. Among 2789 retrieved articles, 380 studies met inclusion criteria. Extracted data included IIM subtype, cohort type, sample size and study design. Registry-based investigations constituted 10.0% of total publications, indicating significant potential for duplication bias. The over-representation of specific cohorts was evident, particularly from China, Japan and the USA, with 33.4% from Asia, 16.58% from Europe and 6.84% from North America. Current myositis research demonstrates substantial dependence on a restricted set of study populations, with limited geographic and demographic diversity. The findings underscore the critical need for broader representation and transparent reporting of cohort sources in myositis research. Promoting rigorous standards in cohort referencing and fostering diverse registries are critical steps towards reducing systemic research biases and enhancing equitable representation across patient populations in IIM.