A trial design that generates only ''positive'' results.

In this article, we test the hypothesis that randomized clinical trials of acupuncture for pain with certain design features (A + B versus B) are likely to generate false positive results. Based on electronic searches in six databases, 13 studies were found that met our inclusion criteria. They all suggested that acupuncture is effected (one only showing a positive trend, all others had significant results). We conclude that the 'A + B versus B' design is prone to false positive results and discuss the design features that might prevent or exacerbate this problem.