A systematic review brings together the results of individual studies that answer a focused clinical question using rigorous research methods. It is common for systematic reviews to include a statistical procedure called meta-analysis to estimate the overall size of the effect and its precision. When well-conducted, systematic reviews are a useful source of evidence to guide physiotherapy practice and should be used in preference to individual studies.
Unfortunately, not all systematic reviews are well-conducted. This means that clinicians need to be able to identify reviews that are credible and contain effect estimates that they can be confident about. The Journal of the American Medical Association (JAMA) Users’ Guides to the Medical Literature provide an excellent framework for how to read systematic reviews that focus on questions about treatment effectiveness and apply the results to patient care. This post briefly summarises the Users’ Guide and provides a link to full-text.
The first judgement to make is whether the review has used credible methods. Skim reading the review to answer four questions will help to identify how credible the review methods are. The four questions are:
- did the review explicitly address a relevant clinical question?
- was the search for relevant studies exhaustive?
- were selection and assessments of studies reproducible?
- did the review present results that are ready for clinical application?
This process will help the physiotherapist to decide whether it is worthwhile to read the systematic review in more detail.
The second judgement to make is how confident you are about the estimates of effect. The Grading of Recommendations Assessment, Development and Evaluation (or “GRADE”) is a framework to evaluate the certainty of evidence in systematic reviews. The six questions to help physiotherapists decide on the quality of the evidence in a review, and hence how confident they can be about the effect estimates are:
- how serious is the risk of bias in the body of evidence?
- are the results consistent across studies?
- how precise are the results?
- do the results directly apply to my patient?
- is there concern about reporting bias?
- are there reasons to increase the confidence rating?
This process will help the physiotherapist to decide whether it is worthwhile to apply the results of the systematic review in clinical practice.
These processes to confirm credibility and confidence in systematic reviews, along with some clinical examples, are explained in full in the full-text for the Users’ Guide:
Murad MH, et al. How to read a systematic review and meta-analysis and apply the results to patient care: users’ guides to the medical literature. JAMA 2014;312(2):171-9
Your ability to read scientific articles reporting the results of systematic reviews will improve with practice. Make the commitment to read at least one article per month and share your reading with the global physiotherapy community in #MyPTArticleOfTheMonth.