Supplementary Material for: Participant heterogeneity of psoriasis interventional trials

Introduction: Participant heterogeneity as a part of clinical heterogeneity has been proved to alter the intervention efficacy, however, factors associated with participant heterogeneity in psoriasis randomized clinical trials (RCTs) are not clear. This study set out to explore participant heterogeneity of randomized clinical trials (RCTs) in psoriasis represented by participant adherence.
Methods: A systematic search of the scientific literature was performed for interventional psoriasis RCTs within published English-language articles from peer-reviewed journals and registered trials in clinical trials registries on July 20, 2021, using 3 databases and 4 registries. Meta-analyses were carried out to calculate the risk ratio (RR) of participant adherence in the intervention and control groups.
Results: A total of 1,714 trials met our inclusion criteria. Factors associated with overall high withdrawal rate were unique between countries with different national incomes. The participant adherence ratio between intervention and control groups was also distinctly influenced by the national income of the trial-conducted country. In low and middle-income countries, the withdrawal ratio was relatively constant, while for trials conducted in high-income countries, the results were altered by compliance reporting, number of participants, disease severity, and country. Moreover, trials conducted in low and middle-income countries tended to have better basal participant adherence.
Conclusions: Our study has revealed the unexpected participant heterogeneity brought by national income in psoriasis RCTs worldwide. Results from high-income countries should be interpreted carefully and rigorously designed single-country trials are always needed for developing local clinical management.