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. 2014 Mar 26:3:77.
doi: 10.12688/f1000research.3784.1. eCollection 2014.

Prevalence of primary outcome changes in clinical trials registered on ClinicalTrials.gov: a cross-sectional study

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Prevalence of primary outcome changes in clinical trials registered on ClinicalTrials.gov: a cross-sectional study

Sreeram Ramagopalan et al. F1000Res. .

Abstract

Background: An important principle in the good conduct of clinical trials is that a summary of the trial protocol, with a pre-defined primary outcome, should be freely available before the study commences. The clinical trials registry ClinicalTrials.gov provides one method of doing this, and once the trial is registered, any changes made to the primary outcome are documented. The objectives of this study were: to assess the proportion of registered trials on ClinicalTrials.gov that had the primary outcome changed; to assess when the primary outcome was changed in relation to the listed study start and end dates and to assess whether the primary outcome change had any relation to the study sponsor.

Methods: A cross-sectional analysis of all interventional clinical trials registered on ClinicalTrials.gov as of 25 October 2012 was performed. The main outcome was any change made to the initially listed primary outcome and the time of the change in relation to the trial start and end date.

Findings: Our analysis showed that 28229 of 89204 (31.7%) registered studies had their primary outcome changed. Industry funding was associated with all primary outcome changes, odds ratio (OR)= 1.36, 95% confidence interval (CI)=1.31-1.41, p<0.001; with primary outcome changes after study start date OR=1.37, 95% CI=1.32-1.42, p<0.001; with primary outcome changes after primary completion date OR=1.84, 95% CI=1.75-1.94, p<0.001 and with primary outcome changes after study completion date OR=1.82, 95% CI=1.73-1.91, p<0.001. Conclusions A significant proportion of interventional trials registered on ClinicalTrials.gov have their primary outcomes altered after the listed study start and completion dates. These changes are associated with funding source.

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Conflict of interest statement

Competing interests: The authors declare no competing interests.

References

    1. Pocock SJ: Clinical trials: a practical approach. Wiley. 1983. Reference Source
    1. Zarin DA, Tse T, Williams RJ, et al. : The ClinicalTrials.gov results database--update and key issues. N Engl J Med. 2011;364(9):852–860 10.1056/NEJMsa1012065 - DOI - PMC - PubMed
    1. DeAngelis CD, Drazen JM, Frizelle FA, et al. : Clinical trial registration: a statement from the International Committee of Medical Journal Editors. JAMA. 2004;292(11):1363–1364 10.1001/jama.292.11.1363 - DOI - PubMed
    1. Zarin DA, Keselman A: Registering a clinical trial in ClinicalTrials.gov. Chest. 2007;131(3):909–912 10.1378/chest.06-2450 - DOI - PubMed
    1. Chan AW, Hróbjartsson A, Haahr MT, et al. : Empirical evidence for selective reporting of outcomes in randomized trials: comparison of protocols to published articles. JAMA. 2004;291(20):2457–2465 10.1001/jama.291.20.2457 - DOI - PubMed