What is a rapid review? A methodological exploration of rapid reviews in Health Technology Assessments

Commissioners of Health Technology Assessments require timely reviews to attain efficacious decisions on healthcare and treatments. In recent years, there has been an emergence of 'rapid reviews' within Health Technology Assessments; however, there is no known published guidance or agreed methodology within recognised systematic review or Health Technology Assessment guidelines. In order to answer the research question 'What is a rapid review and is methodology consistent in rapid reviews of Health Technology Assessments?', a study was undertaken in a sample of rapid review Health Technology Assessments from the Health Technology Assessment database within the Cochrane Library and other specialised Health Technology Assessment databases to investigate similarities and/or differences in rapid review methodology utilised.

In a targeted search to obtain a manageable sample of rapid reviews, the Health Technology Assessment database of The Cochrane Library and six international Health Technology Assessment databases were searched to locate rapid review Health Technology Assessments from 2000 onwards. Each rapid review was examined to investigate the individual methodology used for searching, inclusion screening, quality assessment, data extraction and synthesis. Methods of each rapid review were compared to investigate differences and/or similarities in methodologies used, in comparison with recognised methods for systematic reviews.

Forty-six full rapid reviews and three extractable summaries of rapid reviews were included. There was a wide diversity of methodology, with some reviews utilising well-established systematic review methods, but many others diversifying in one or more areas, that is searching, inclusion screening, quality assessment, data extraction, synthesis methods, report structure and number of reviewers. There was a significant positive correlation between the number of recommended review methodologies utilised and length of time taken in months.

Despite the number of rapid reviews published within Health Technology Assessments over recent years, there is no agreed and tested methodology and it is unclear how rapid reviews differ from systematic reviews. In a sample of Health Technology Assessment rapid reviews from 2000 to 2011, there was a wide diversity of methodology utilised in all aspects of rapid reviews. There is scope for wider research in this area to investigate the diversity of methods in more depth during each stage of the rapid review process, so that eventually recommendations could be made for clear and systematic methods for rapid reviews, thus facilitating equity and credibility of this type of important review methodology.