Placebo design, reporting compliance, and methodological problems in randomized, placebo-controlled trials of Chinese...

This cross-sectional study aimed to characterize the design, application, and reporting standards of Chinese herbal medicine placebos (CHM-placebos) in randomized controlled trials (RCTs) published between 2018 and 2025.

We searched the Web of Science database for RCTs involving Chinese herbal medicine (CHM) and matching placebos published from January 2018 to September 2025. Methodological quality was assessed using Risk of Bias Instrument for Use in Systematic reviews for Randomized Controlled trials (ROBUST-RCT). Reporting compliance was evaluated according to the Consolidated Standards of Reporting Trials (CONSORT) Extension for Chinese Herbal Medicine Formulas (CONSORT-CHM). Descriptive statistics summarized features of CHM-placebos' design.

A total of 136 trials were included. Methodological assessment revealed that "Allocation concealment" had the highest risk (definitely high risk: 4%, probably high risk: 19%). Reporting compliance with CONSORT-CHM placebo-specific items was low, only 16 trials (11.76%) fully reported the name and amount of each ingredient, 6 trials (4.41%) trials reported quality control and safety assessments, and 9 trials (6.62%) provided complete production information. Manufacturers' information was reported in 90 trials (66.18%). 33 trials (24.26%) reported that their CHM-placebos contained traditional Chinese medicine ingredients, with two trials using placebos composed entirely of TCM.

Deficiencies persist in the CHM-placebos' design and reporting, especially regarding compositional transparency and quality verification. The use of CHM-placebos containing TCM ingredients challenges the fundamental principle of pharmacological inertness.