The review had clear inclusion criteria for participants, interventions and outcomes. The inclusion criteria for study designs specified clinical trials, but a number of comparative observational studies were included. This meant that the review was not restricted to the best available evidence to determine efficacy. The authors searched a range of relevant sources and made some efforts to locate unpublished studies; risk of publication bias was not assessed. The review was limited to English language studies, so relevant studies published in other languages could have been omitted (language bias). Although data extraction was conducted by two independent reviewers, the methods used for study selection were not reported, so the risk of errors or bias at this stage was uncertain. Some relevant details of included studies were reported.
The authors did not report that they assessed the quality of the included studies. This means that the reliability of the studies, and the synthesis based on them, is uncertain. Most of the included studies were observational studies, inherently more prone to bias than randomised trials. There were some differences between treatment groups at baseline, which could reflect the presence of selection bias. Studies of different designs were pooled by meta-analysis, which may not have been appropriate. Heterogeneity was assessed and no significant statistical heterogeneity was found.
The authors stated that percutaneous coronary intervention with drug-eluting stents was safe; safety was not explicitly defined in the paper, and this conclusion is not in line with all the evidence presented, particularly the higher rate of major adverse cardiac events in the percutaneous coronary intervention group. This, together with weaknesses in the evidence base and review methods, particularly lack of quality assessment, means that the authors' conclusions should be treated with caution.