Does random participant assignment cause fewer benefits in research participants? Systematic review of partially randomized acupuncture trials.

OBJECTIVES: It has been suggested that the random assignment of participants does not cause harm to patients in clinical trials. However, in a recent study, patient preference affected the health outcome of the patients. It can therefore be assumed that patients who are allocated at random may be affected by placebo effects that are associated with the treatment of their choice. The aim of this study was to determine whether random participant assignment in acupuncture trials causes fewer benefits to the participants. DATA SOURCES: The following computerized databases were searched from their inception to December 2008: MEDLINE, SCOPUS, CINAHL, Cochrane Registered Trial, British Library Direct, and Google Scholar. Review methods: This was a systematic review of partially randomized acupuncture trials with adequate randomization generation and concealment of participant group allocation as well as large enough sample sizes to satisfy a power calculation. RESULTS: Six (6) trials that met the selection criteria were included. The randomized acupuncture group comprised patients with different demographics and health outcomes than the observational group. Substantial numbers of eligible patients refused to participate in the randomization. The baseline patient characteristics were different between the randomized acupuncture group and the observational group. The proportion of patients who dropped out of or withdrew from the study was also different between the groups, with significantly more dropping out from the observational group than the randomized group. Patients in the observational group had significantly better health outcomes than patients in the randomized group, with a standardized mean difference of 0.06 (95% confidence interval 0.03-0.09). CONCLUSIONS: We found that patients who were randomly assigned to treatment groups in acupuncture trials had fewer health benefits than those who were nonrandomly assigned.