Methodological challenges when performing a systematic review.

Well-conducted systematic reviews can provide a foundation upon which to base educational curricula, practice guidelines and healthcare policy. We aim to provide an overview of important methodological issues that need to be addressed during the five phases of performing a systematic review. 1. The specific problems to be addressed by the systematic review need to be formulated as clear, unambiguous and structured question/s. 2. Literature from multiple resources should be searched to avoid publication biases, as positive outcomes are more likely to be published than null/negative results. 3. The quality of selected articles should be assessed using a checklist, while the reliability of graders, as well as the quality of the checklist, needs to be established a priori. 4. Statistical heterogeneity needs to be assessed to determine if a meta-analysis is appropriate to pool the data. If not, a narrative synthesis of the evidence/overall findings needs to be performed within a clinical context.