Do acupuncture trials have lower risk of bias over the last five decades? A methodological study of 4 715 randomized controlled trials.

Although improvements concerning unclear risk were observed for random sequence generation and selective reporting, major issues remain for allocation concealment and blinding. It is imperative to use valid randomization, specify how it is conducted, and try to test for selection bias and the success of masking by using the Berger Exner test.