Interventional single-arm trials (SATs) are increasingly utilized as evidence sources; however, questions remain about their validity and their rightful place within the evidence hierarchy. A comprehensive meta-epidemiological study was conducted to examine whether SATs differ systematically from single-arm cohort studies regarding outcomes and the extent of between-study heterogeneity.
Methodology and Data Collection
The study reviewed systematic reviews of pharmacological interventions published in 2023, selecting those that included both SATs and observational single-arm studies. For each systematic review, the researchers performed subgroup meta-analyses focusing on dichotomous efficacy outcomes to assess effect sizes, heterogeneity levels, and differences between the groups. Additionally, a sensitivity analysis was carried out by excluding clinically heterogeneous primary studies to determine the consistency of the results.
Findings and Heterogeneity
From 66 systematic reviews incorporating single-arm studies, 13 provided meta-analyses of dichotomous efficacy outcomes. The analysis indicated no significant risk difference between SATs and single-arm cohort studies, with a risk difference of -0.020 (95% CI: -0.092 to 0.052, p=0.59). In the sensitivity analysis, a trend towards higher effects was observed in single-arm cohort studies, though the difference remained non-significant (risk difference: -0.071, 95% CI: -0.161 to 0.019, p=0.12). Both SATs and cohort studies exhibited high levels of between-study heterogeneity, with SATs having a median I² of 54.8% (range 11.3-91.0) and cohort studies a median I² of 77.2% (range 0-94.7), persisting even after the sensitivity analysis.
Key inferences include:
- SATs provide effect sizes similar to those obtained from single-arm cohort studies in pharmacological interventions.
- The significant heterogeneity observed suggests potential biases related to study execution across both study designs.
- Excluding clinically heterogeneous studies does not substantially reduce the variability, indicating other sources of heterogeneity.
The findings highlight the complexity of relying on SATs for evidence due to the considerable variability among studies. Although SATs and cohort studies yield comparable outcomes, the persistent high heterogeneity points to possible methodological issues or biases that may affect the reliability of the results.
Advancing research in this area is crucial to confirm these observations. Future studies should incorporate larger sample sizes and employ additional methodological techniques to better understand the validity of single-arm designs. Enhancing the methodological rigor of SATs could solidify their role in evidence generation, assisting healthcare professionals and policymakers in making informed, evidence-based decisions.
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