Impact of covert duplicate publication on meta-analysis: a case study

Abstract Objective: To quantify the impact of duplicate data on estimates of efficacy. Design: Systematic search for published full reports of randomised controlled trials investigating ondansetron's effect on postoperative emesis. Abstracts were not considered. Data sources: Eighty four trials...

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Bibliographic Details
Published in:	BMJ 1997-09, Vol.315 (7109), p.635-640
Main Authors:	Tramèr, Martin R, Reynolds, D John M, Moore, R Andrew, McQuay, Henry J
Format:	Article
Language:	eng
Subjects:	Analysis Antiemetics Antiemetics - therapeutic use Biological and medical sciences Confidence interval Data tables Digestive system Dosage Duplicate Publication as Topic Experimentation Health care Humans Medical research Medical sciences Meta analysis Meta-Analysis as Topic Nausea Ondansetron - therapeutic use Pharmacology. Drug treatments Placebos Postoperative Complications - prevention & control Postoperative nausea Randomized Controlled Trials as Topic Treatment Outcome Vomiting Vomiting - prevention & control
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Summary:	Abstract Objective: To quantify the impact of duplicate data on estimates of efficacy. Design: Systematic search for published full reports of randomised controlled trials investigating ondansetron's effect on postoperative emesis. Abstracts were not considered. Data sources: Eighty four trials (11 980 patients receiving ondansetron) published between 1991 and September 1996. Main outcome measures: Percentage of duplicated trials and patient data. Estimation of antiemetic efficacy (prevention of emesis) of the most duplicated ondansetron regimen. Comparison between the efficacy of non-duplicated and duplicated data. Results: Data from nine trials had been published in 14 further reports, duplicating data from 3335 patients receiving ondansetron; none used a clear cross reference. Intravenous ondansetron 4 mg versus placebo was investigated in 16 reports not subject to duplicate publication, three reports subject to duplicate publication, and six duplicates of those three reports. The number needed to treat to prevent vomiting within 24 hours was 9.5 (95% confidence interval 6.9 to 15) in the 16 non-duplicated reports and 3.9 (3.3 to 4.8) in the three reports which were duplicated (P
ISSN:	0959-8138 0959-8146 1468-5833 1756-1833