Strengths and limitations of systematic reviews of drug trials: The biostatistical perspective

Some thousands of randomized controlled trials are published each year. But clinicians are pinched for time to study the literature. Hence, systematic reviews are important to combine the results for a specific medical question. Meta-analysis is only a statistical method that was used in systematic reviews to combine the results of individual studies. Our aim is to discuss the strengths and potential pitfalls of systematic reviews on the basis of five examples from the literature. We focus on aspects limiting the strength of systematic reviews, such as publication bias, imputation of missing data, and the use of inappropriate statistical methods. Although systematic reviews are key to summarizing evidence, meta-analyses of drug trials should be read with a healthy portion of scepticism.