Reporting bias

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In epidemiology, reporting bias is defined as "selective revealing or suppression of information" by subjects (for example about past medical history, smoking, sexual experiences).[1]

By extension, in empirical research in general, the term reporting bias may be used to refer to a tendency to under-report unexpected or undesirable experimental results, attributing the results to sampling or measurement error, while being more trusting of expected or desirable results, though these may be subject to the same sources of error. In this context, reporting bias can eventually lead to a status quo where multiple investigators discover and discard the same results, and later experimenters justify their own reporting bias by observing that previous experimenters reported different results. Thus, each incident of reporting bias can make future incidents more likely. [2][3] Sociologist Christopher B. Doob refers to this practice as selective reporting in explaining the Power of the Press and defines it as biased coverage of news issues that promotes corporate interests and downplays, denigrates, or ignores issues and groups challenging these issues.[4]

Case study[edit]

Litigation brought upon by consumers and health insurers against Pfizer for the fraudulent sales practices in marketing of the drug gabapentin in 2004 revealed a comprehensive publication strategy that employed elements of reporting bias.[5] Spin was used to put emphasis on favorable findings that favored gabapentin, and also to explain away unfavorable findings towards the drug. In this case, favorable secondary outcomes became the focus over the original primary outcome, which was unfavorable. Other changes found in outcome reporting include the introduction of a new primary outcome, failure to distinguish between primary and secondary outcomes, and failure to report one or more protocol-defined primary outcomes.[6]

The decision to publish certain findings in certain journals is another strategy.[5] Trials with statistically significant findings were generally published in academic journals with higher circulation more often than trials with nonsignficant findings. Timing of publication results of trials was influenced, in that the company tried to optimize the timing between the release of two studies. Trials with nonsignificant findings were found to be published in a staggered fashion, as to not have two consecutive trials published without salient findings. Ghost authorship was also an issue, where professional medical writers who drafted the published reports were not properly acknowledged.

Fallout from this case is still being settled by Pfizer in 2014, 10 years after the initial litigation.[7]

Types of reporting bias[edit]

  • Publication bias: The publication or nonpublication of research findings, depending on the nature and direction of the results.
  • Time lag bias: The rapid or delayed publication of research findings, depending on the nature and direction of the results.
  • Multiple (duplicate) publication bias: The multiple or singular publication of research findings, depending on the nature and direction of the results.
  • Location bias: The publication of research findings in journals with different ease of access or levels of indexing in standard databases, depending on the nature and direction of results.
  • Citation bias: The citation or non-citation of research findings, depending on the nature and direction of the results.
  • Language bias: The publication of research findings in a particular language, depending on the nature and direction of the results.
  • Outcome reporting bias: The selective reporting of some outcomes but not others, depending on the nature and direction of the results.[8]

See also[edit]


  1. ^ Porta, Miquel, ed. (5 June 2008). A Dictionary of Epidemiology. Oxford University Press. p. 275. ISBN 978-0-19-157844-1. Retrieved 27 March 2013. 
  2. ^ Green S, Higgins S, editors: Glossary. Cochrane Handbook for Systematic Reviews of Interventions 4.2.5.
  3. ^ McGauran N, Wieseler B, Kreis J, Schüler YB, Kölsch H, Kaiser T. Reporting bias in medical research - a narrative review. Trials. 2010; 11:37. doi:10.1186/1745-6215-11-37
  4. ^ Doob, C. B. (2013). Social inequality and social stratification in US society. Upper Saddle River, NJ: Pearson.
  5. ^ a b Vedula, SS; Goldman, PS; Rona, IJ; Greene, TM; Dickersin, K (2012). "Implementation of a publication strategy in the context of reporting biases. A case study based on new documents from Neurontin litigation". Trials 13 (136). doi:10.1186/1745-6215-13-136. PMID 22888801. 
  6. ^ Vedula, SS; Bero, L; Scherer, RW; Dickersin, K (2009). "Outcome reporting in industry-sponsored trials for gabapentin for off-label use". N Eng J Med 361 (120): 1963–1971. doi:10.1056/NEJMsa0906126. PMID 19907043. 
  7. ^ Stempel, Jonathan (06-02-2014). "Pfizer to pay $325 million in Neurontin settlement". Reuters. Retrieved 2014-08-24.  Check date values in: |date= (help)
  8. ^ Sterne, J.; Egger, M.; Moher, D. (2008). "Addressing reporting biases". In Higgins, J. P. T.; Green, S. Cochrane handbook for systematic reviews of interventions. Chichester: Wiley. pp. 297–334. ISBN 978-0-470-69951-5.