Background: Adaptive design (AD) allows preplanned modifications to an ongoing trial based on an interim analysis of data collected from participants, making it more cost-effective and time efficient. Poor reporting of randomized controlled trials (RCTs) with AD can make trial findings difficult to interpret; therefore, authors can utilize 2020 AD Consolidated Standards of Reporting Trials 2010 extension (ACE) statement for reporting their trials.

Objectives: To evaluate the reporting quality of RCTs that use an AD based on the 2020 ACE guidelines and to identify factors associated with better reporting quality.

Methods: Five electronic databases were searched until November 1, 2022, for adaptive clinical trials. Multivariable linear regression analysis was performed to investigate potential predictors.

Results: In our study, 109 RCTs were included. The mean compliance rate for the ACE checklist items was 69.75% ± 16.02. Key methodological items including allocation concealment and its implementations were poorly reported. Also, the reporting of checklist items related to the conduct of interim analyzes was suboptimal. Multivariable regression analysis showed better reporting quality of AD with trial registration, non-industry affiliation (first author), a sample size of > 100, general medical journal type, publication date (≥2020), funding, and disclosure of the number of interims analyze.

Conclusion: Our study showed that RCTs with AD had suboptimal reporting of 2020 ACE checklist items, particularly AD-specific items. Stricter adherence to the ACE guideline is necessary to improve their reporting quality.