How to do a systematic review.

High quality up-to-date systematic reviews are essential in order to help healthcare practitioners and researchers keep up-to-date with a large and rapidly growing body of evidence. Systematic reviews answer pre-defined research questions using explicit, reproducible methods to identify, critically appraise and combine results of primary research studies. Key stages in the production of systematic reviews include clarification of aims and methods in a protocol, finding relevant research, collecting data, assessing study quality, synthesizing evidence, and interpreting findings. Systematic reviews may address different types of questions, such as questions about effectiveness of interventions, diagnostic test accuracy, prognosis, prevalence or incidence of disease, accuracy of measurement instruments, or qualitative data. For all reviews, it is important to define criteria such as the population, intervention, comparison and outcomes, and to identify potential risks of bias. Reviews of the effect of rehabilitation interventions or reviews of data from observational studies, diagnostic test accuracy, or qualitative data may be more methodologically challenging than reviews of effectiveness of drugs for the prevention or treatment of stroke. Challenges in reviews of stroke rehabilitation can include poor definition of complex interventions, use of outcome measures that have not been validated, and poor generalizability of results. There may also be challenges with bias because the effects are dependent on the persons delivering the intervention, and because masking of participants and investigators may not be possible. There are a wide range of resources which can support the planning and completion of systematic reviews, and these should be considered when planning a systematic review relating to stroke.