In the era of evidence-based public health, systematic reviews are becoming more and more popular and being used more often both as a method of study and as a source of evidence for program and policy development. Thus, public health students and professionals should know and understand the concept, process and value of systematic reviews on different public health topics. Due to higher level of evidence ranking, findings from the systematic reviews are being used more often for policy and program development. Initially, systematic reviews only included findings from the randomized controlled trials, but now it also includes highquality quasi-experimental studies as randomized control trials are not feasible in all public health topics. Primary purpose of this paper is to orient public health students and professionals about systematic review and thus presented in frequently asked questions and response format.
What is a systematic review?A systematic review is a high-level overview of primary research on a particular research question that tries to identify, select, synthesize and appraise all high quality research
Systematic Reviews in Public HealthPaudel D 1 evidence relevant to that question in order to answer it. (1) The purpose of a systematic review is to sum up the best available research on a specific question. This is done by synthesizing the results of several studies using metaanalysis. (2) Meta-analysis is the statistical analysis of the data/results from studies included in a systematic review to produce an overall, pooled result. (3) Why systematic reviews?A systematic review answers the same research question and that conforms to set criteria based on the review of the methods and results of all individual studies; it, therefore, provides higher level of evidence than from a primary study.Though hierarchy of evidence is a matter of debate (4), evidence from the systematic reviews are considered "superior " compared to those from the randomized control trial, cohort study, case-control study, cross-sectional study and case study. Table 1 shows the strengths of evidence from different studies by the types of the research questions.