Quality of systematic reviews of observational nontherapeutic studies.
BACKGROUND
High-quality epidemiologic research is essential in reducing chronic diseases. We analyzed the quality of systematic reviews of observational nontherapeutic studies.


METHODS
We searched several databases for systematic reviews of observational nontherapeutic studies that examined the prevalence of or risk factors for chronic diseases and were published in core clinical journals from 1966 through June 2008. We analyzed the quality of such reviews by using prespecified criteria and internal quality evaluation of the included studies.


RESULTS
Of the 145 systematic reviews we found, fewer than half met each quality criterion; 49% reported study flow, 27% assessed gray literature, 2% abstracted sponsorship of individual studies, and none abstracted the disclosure of conflict of interest by the authors of individual studies. Planned, formal internal quality evaluation of included studies was reported in 37% of systematic reviews. The journal of publication, topic of review, sponsorship, and conflict of interest were not associated with better quality. Odds of formal internal quality evaluation (odds ratio [OR], 1.10 per year; 95% confidence interval [CI], 1.02-1.19) and either planned, formal internal quality evaluation or abstraction of quality criteria of included studies (OR, 1.17 per year; 95% CI, 1.08-1.26) increased over time, without positive trends in other quality criteria from 1990 through June 2008. Systematic reviews with internal quality evaluation did not meet other quality criteria more often than those that ignored the quality of included studies.


CONCLUSIONS
Collaborative efforts from investigators and journal editors are needed to improve the quality of systematic reviews.
Minnesota Evidence-based Practice Center, University of Minnesota School of Public Health, D351 Mayo (MMC 197), 420 Delaware St SE, Minneapolis, MN 55455, USA. shaml005@umn.edu
Tatyana
T
Shamliyan
Robert L
RL
Kane
Stacy
S
Jansen
D002908:Chronic Disease / Q000453:epidemiology*; D016265:Conflict of Interest; D016021:Epidemiologic Studies; D010506:Periodicals as Topic; D011643:Publishing / Q000592:standards; D012106:Research / Q000191:economics / Q000592:standards*; D012196:Review Literature as Topic; D012307:Risk Factors