Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Meta-Analysis
. 2006 Nov;244(5):668-76.
doi: 10.1097/01.sla.0000225356.04304.bc.

Comparison of effects in randomized controlled trials with observational studies in digestive surgery

Satoru Shikata  1 , Takeo Nakayama, Yoshinori Noguchi, Yoshinori Taji, Hisakazu Yamagishi
Affiliations
Meta-Analysis

Comparison of effects in randomized controlled trials with observational studies in digestive surgery

Satoru Shikata et al. Ann Surg. 2006 Nov.

Abstract

Objectives: To compare the results of randomized controlled trials versus observational studies in meta-analyses of digestive surgical topics.

Summary background data: While randomized controlled trials have been recognized as providing the highest standard of evidence, claims have been made that observational studies may overestimate treatment benefits. This debate has recently been renewed, particularly with regard to pharmacotherapies.

Methods: The PubMed (1966 to April 2004), EMBASE (1986 to April 2004) and Cochrane databases (Issue 2, 2004) were searched to identify meta-analyses of randomized controlled trials in digestive surgery. Fifty-two outcomes of 18 topics were identified from 276 original articles (96 randomized trials, 180 observational studies) and included in meta-analyses. All available binary data and study characteristics were extracted and combined separately for randomized and observational studies. In each selected digestive surgical topic, summary odds ratios or relative risks from randomized controlled trials were compared with observational studies using an equivalent calculation method.

Results: Significant between-study heterogeneity was seen more often among observational studies (5 of 12 topics) than among randomized trials (1 of 9 topics). In 4 of the 16 primary outcomes compared (10 of 52 total outcomes), summary estimates of treatment effects showed significant discrepancies between the two designs.

Conclusions: One fourth of observational studies gave different results than randomized trials, and between-study heterogeneity was more common in observational studies in the field of digestive surgery.

PubMed Disclaimer

Figures

None
FIGURE 1. Summary profile of search for meta-analyses of randomized controlled trials.
None
FIGURE 2. Summary profile of search for observational studies.
None
FIGURE 3. Comparison of primary outcomes between observational studies and randomized controlled trials. This figure is based on data from 13 review articles and 10 meta-analyses of observational studies by the authors. OR, odds ratio; RR, relative risk; CI, confidence interval. *Outcome reporting relative risk rather than odds ratio.
See this image and copyright information in PMC

Comment in

References

    1. Streptomycin treatment of pulmonary tuberculosis: a Medical Research Council investigation. BMJ. 1948;2:769–782. - PMC - PubMed
    1. Preventive Services Task Force. Guide to Clinical Preventive Services: Report of the U.S. Preventive Services Task Force, 2nd ed. Baltimore: Williams & Wilkins, 1996.
    1. Chalmers TC, Matta RJ, Smith H Jr, et al. Evidence favoring the use of anticoagulants in the hospital phase of acute myocardial infarction. N Engl J Med. 1977;297:1091–1096. - PubMed
    1. Sacks HS, Chalmers TC, Smith H Jr. Randomized versus historical controls for clinical trials. Am J Med. 1982;72:233–240. - PubMed
    1. Colditz GA, Miller JN, Mosteller F. How study design affects outcomes in comparisons of therapy. I. Med Stat Med. 1989;8:441–454. - PubMed

Publication types

MeSH terms

LinkOut - more resources