Acupuncture and chronic pain: a criteria-based meta-analysis. A literature search revealed 51 controlled clinical studies on the effectiveness of acupuncture in chronic pain. These studies were reviewed using a list of 18 predefined methodological criteria. A maximum of 100 points for study design could be earned in four main categories: (a) comparability of prognosis, (b) adequate intervention, (c) adequate effect measurement and (d) data presentation. The quality of even the better studies proved to be mediocre. No study earned more than 62% of the maximum score. The results from the better studies (greater than or equal to 50% of the maximum score) are highly contradictory. The efficacy of acupuncture in the treatment of chronic pain remains doubtful. 