Systematic review and network meta-analysis in health technology assessment.

Conducting systematic review and meta-analysis (SR/MA) is a standard process for establishing evidences for health technology assessment. Quality assessment of studies included in SR/MA and SR/MA studies should be considered. This article provides recommendations on tools used for assessing the quality of studies included in each SR/MA and the quality of SR/MA. For assessing the quality of randomized controlled trial, we recommend a tool called "Risk of Bias", which focuses on random generation, allocation concealment, blinding and outcome reporting. For assessing the quality of observational study, the Newcastle Ottawa Scale (NOS) is recommended. The NOS consists of three different dimensions-selection, comparability and outcomes or exposure. Another tool which is recommended is the Down and Black scale. It focuses on the quality of reporting, validity, bias and confounding, and power of study. For assessing the quality of SR/MA, we recommend to use a checklist developed by Klassen et al, covering well-defined question, inclusion criteria, comprehensiveness, quality of included studies, reproducibility, and external validity. This article also provides a fundamental of network meta-analysis that should be considered where no direct evidence exists or when there is a need to compare multiple interventions at the same time.