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Editorials |

Metabias: A Challenge for Comparative Effectiveness Research

Steven Goodman, MD, MHS, PhD; and Kay Dickersin, MA, PhD
[+] Article, Author, and Disclosure Information

From Johns Hopkins University, Baltimore, MD 21205.

Potential Conflicts of Interest: None disclosed. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M11-1186.

Requests for Single Reprints: Steven Goodman, MD, MHS, PhD, Johns Hopkins University, Oncology Biostatistics, 550 North Broadway, Suite 1103, Baltimore, MD 21205; e-mail, sgoodman@jhmi.edu.

Current Author Addresses: Dr. Goodman: Johns Hopkins University, Oncology Biostatistics, 550 North Broadway, Suite 1103, Baltimore, MD 21205.

Dr. Dickersin: Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205.

Ann Intern Med. 2011;155(1):61-62. doi:10.7326/0003-4819-155-1-201107050-00010
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Metabias poses unique challenges for comparative effectiveness research and evidence-based healthcare. Dechartres and colleagues' study in this issue raises the specter of a new metabias that is particularly troubling: that associated with single-center studies. The editorialists explore the implications of these findings and the conundrum that they pose.

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Possible reason for larger effect of single center trials
Posted on July 8, 2011
Stephen J Seligman
New York Medical College
Conflict of Interest: None Declared

The editorial by Goodman and Dickerson (1) discusses the meta- epidemiologic study of Dechartres et al (2) that found a 26% larger effect in single center compared with multicenter trials. The editorial acknowledges that, lacking an independent gold standard, it is not possible to decide whether one or both types of studies are biased. However, multicenter trials are susceptible to intercenter variations absent in single center trials. Of necessity all of these variations cannot improve the reliability of the outcomes. Accordingly, the possibility that single center trials show larger effects is not surprising.


1 Goodman S, Dickersin K. Metabias: a challenge for comparative effectiveness research. Ann Intern Med. 2011;155:61-62.

2 Dechartres A, Boutron I, Trinquart L, Charles P, Ravaud P. Single- Center Trials Show Larger Treatment Effects Than Multicenter Trials: Evidence From a Meta-epidemiologic Study. Ann Intern Med. 2011;155:39-51.

Conflict of Interest:

None declared

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