Background and objectives: Subject dropout rates in placebo-controlled randomized clinical trials (RCTs) of antipsychotics are high. The missing values due to dropout represent a potential source of bias in clinical trials. We aimed to identify the potential factors affecting subject dropout in atypical antipsychotics RCTs by conducting a meta-analysis.
Methods: Placebo-controlled RCTs for atypical antipsychotics using positive and negative syndrome scale (PANSS) as a psychiatric assessment scale were selected by database search. The potential factors affecting subject dropout, such as publication year, study design, and operational factors, were analyzed by meta-regression.
Results: Forty-seven placebo controlled RCTs of atypical antipsychotics of which results were published between 1993 and 2018 were identified through the database search. In the multivariate meta-regression analysis, earlier publication year, older age of subjects, and longer study duration were significantly associated with high subject dropout rates in placebo-controlled clinical trials of atypical antipsychotics.
Conclusion: Subject dropout rates in clinical trials of atypical antipsychotics published between 1993 and 2018 year decreased over time. Study duration should be taken into consideration when designing future studies, where short study periods yet appropriate for evaluating the efficacy of new atypical antipsychotics are preferable. Additionally, previous medications and the degree of subject satisfaction with antipsychotics might affect subject dropout rate.