The authors stated their review question and the inclusion criteria clearly. The study inclusion criteria stated that it was a prerequisite that the studies were conducted in Western countries. This was justified by the statement that acupuncture is a respected form of treatment in China; this general acceptance may influence patient opinion regarding the effectiveness of acupuncture by enhancing the placebo effect.
The literature search was clearly described although the search dates were omitted. However, the search was not thorough and the authors made no attempt to identify unpublished or grey literature, although textbooks, an acupuncture journal and other relevant sources were searched. This narrow search strategy might have missed relevant studies, thus allowing a selection bias to be introduced; particularly, since the journal chosen for searching was an acupuncture journal, which may have been a biased source. Publication bias was not assessed.
Relevant literature could also have been identified by searching other appropriate databases, such as EMBASE, SIGLE and the NRR, and by contacting experts in the field.
The authors did not report a method for assessing validity. The authors state that acupuncture trials are not double-blind as the clinician administering acupuncture is aware of which is the true treatment, and placebo acupuncture is not an ideal placebo.
The authors did not report details of the study selection, data extraction or validity assessment processes, such as how many of the reviewers were involved, whether the studies were examined independently, whether the reviewers were blinded to the source, and how any disagreements were resolved.
The study details were displayed in two tables that included information relating to sample size, type of headache, brief description of interventions, follow-up, authors' results, and comments. There was no key to explain the abbreviations used in the tables, and it was unclear why the studies were split between two different tables. These data were supplemented by a narrative discussion. A typing error was made in the results section relating to the number of trials investigating the different types of headache. There was limited data on the methodology of the included studies, such as how pain was measured, how the studies classified the treatment as a success or failure, and who performed the acupuncture.
No formal tests for heterogeneity were performed, although the authors stated that the selected studies differed significantly. Despite this, the authors crudely pooled the results of the studies using a method known as 'vote counting'.
The authors' conclusions appear justified based on their crude pooling of results. However, the conclusions must be interpreted with caution given the potential for selection bias, lack of quality assessment, and the heterogeneity of the studies. The review appears to be relevant to the topic area.