Are study design characteristics in single-arm trials comparable with those of their objective performance criteria or performance goals? A scoping review.

Abstract

Single-arm trials (SATs) with objective performance criteria (OPCs) or performance goals (PGs) are increasingly used for regulatory approval of medical devices and other interventions. However, the comparability of study design characteristics between SAT and their external comparator sources remains unclear. This scoping review aimed to evaluate the comparability of study design characteristics between SATs and their matched OPC/PG sources. Scoping review. PubMed, Embase, the Cochrane Library and four Chinese databases-China National Knowledge Infrastructure, Wanfang Data, CQVIP and SinoMed-were searched from inception to 30 April 2026. We included SATs that used one or more OPCs or PGs as external comparators to evaluate safety and/or effectiveness endpoints and reported specific numerical values of OPCs or PGs. Two reviewers independently screened the retrieved records and extracted data using a standardised form. For each included SAT, we retrieved the cited OPC/PG sources and extracted study design characteristics data (age, sex, health conditions, outcome definitions and measurement time points) for comparison. Age and sex were compared using summary t-tests and χ² tests; health conditions were assessed by two clinicians based on eligibility criteria and baseline characteristics. Results were stratified by OPC versus PG. A total of 1243 records were identified, and 133 SATs were included. Most studies used PGs (84, 63.2%); 34 (25.6%) claimed to use OPCs, and 15 (11.3%) could not be classified. Of the 60 age comparisons available from 41 studies, 30 showed statistically significant differences; of the 82 sex comparisons available from 59 studies, 60 showed significant differences. Health conditions, outcome definitions and time points were assessed descriptively in a subset of studies, and discrepancies were also observed. Suboptimal comparability of study design characteristics was observed between SATs and their OPC/PG sources, which might influence the treatment effect estimates. Greater attention to the comparability of study design characteristics in SATs with OPC/PGs may improve the validity of evidence.