Background and objective: To review current practice in the assessment of the quality of original observational studies included in systematic reviews.
Materials and methods: Examination of all systematic reviews identified by a basic PubMed search for the years 1999-2000 (32 reviews) and 2003-2004 (98 reviews). English language systematic reviews published in peer-reviewed journals was the setting. Each review was evaluated for the use of quality assessment of original observational studies and if quality assessment occurred, what type of assessment was used.
Results: Quality assessment occurred in 22% of systematic reviews identified in 1999-2000 compared with 50% of reviews identified from 2003-2004. All earlier reviews devised their own quality assessment criteria, whereas in 2003-2004 10 different quality assessment techniques were identified.
Conclusions: Quality assessment does not routinely occur in systematic reviews of observational studies. Where it does occur, there is no clear consensus in the method used.