Publication bias

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This editable Main Article is under development and subject to a disclaimer.

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## Contents

* 1 Examples
* 2 Frequency of occurrence
* 2.1 Randomized controlled trials
* 2.2 Studies of diagnostic tests
* 3 Detection
* 4 Causes
* 5 Related biases
* 5.1 Language bias
* 5.2 Availability of full text on the Internet
* 5.3 No abstract available (NAA) bias
* 5.4 Selective outcome reporting bias
* 6 Impact of publication bias
* 6.1 Impact on meta-analysis
* 6.2 Impact on the drug approval process
* 6.3 Impact on media coverage of scientific research
* 7 Prevention
* 7.1 Trial registration
* 8 References

In academic journals and scientific journals, publication bias is defined as "the influence of study results on the chances of publication and the tendency of investigators, reviewers, and editors to submit or accept manuscripts for publication based on the direction or strength of the study findings. Publication bias has an impact on the interpretation of clinical trials and meta-analyses. Bias can be minimized by insistence by editors on high-quality research, thorough literature reviews, acknowledgment of conflicts of interest, modification of peer review practices, etc."[1]

Publication bias has been documented to occur.[2]

The small study effect is closely related. The small study effect is the observation that small studies tend to report more positive results.[3][4] This is especially a threat when the original studies in a meta-analysis are less than 50 patients in size.[5]

## Examples[edit]

An example of probable publication bias is in the studies of glucosamine and chondroitin for treatment of osteoarthritis. In an initial meta-analysis, the authors noted evidence of publication bias during examination of the results.[6]

A subsequent large randomized controlled trial[7] and meta-analyses including the large trial were negative.[8][9]

Another example is the selective publication of randomized controlled trials of antidepressants[10] or of positive trials in general[11].

Anecdotal examples include partial publication of results of trails of the antiviral agent oseltamivir for the prevention of influenza.[12]

## Frequency of occurrence[edit]

### Randomized controlled trials[edit]

Publication bias, or bias in interpretation of studies, may occur in 25%[13] to 60% of some types of articles.[14][15][16] Publication bias may be associated with the language the study is published in and may be more common in certain areas of study. In the field of complementary and alternative medicine (CAM), publication bias may be more likely to occur in studies published in languages other than English.[17]

A possible reason is that typical CAM studies are smaller than trials of conventional medicine.[17] According to two European analyses, both including German authors and one from the German Cochrane Center, this bias may be especially prevalent in German publications.[18][19]

Negative studies are less likely to be published[20][21] and have more delays in their publication[22].

### Studies of diagnostic tests[edit]

Publication bias may occur in studies of diagnostic tests.[23] Publication bias may be more of a problem in diagnostic test research than in randomized controlled trials because studies of diagnostic tests can be secondary analyses of databases and do not have to be registered prior to publication.[24]

## Detection[edit]

In meta-analyses of randomized controlled trials, a file drawer[25], a funnel plot analysis[26][27], or a contour enhanced funnel plot[28] may help detect underlying publication bias among the studies in the meta-analysis. However, other factors may cause asymmetry[29] and the interpretation of the graph is subjective and inconsistent[27].

In meta-analysis of diagnostic tests, the effective sample size funnel plot and associated regression test of asymmetry may be used.[30]

## Causes[edit]

Many factors influence publication.[2][31] Publication bias may be due to authors not submitting negative studies for publication.[31] This may especially be true of studies authored by industries with conflicts of interest.[32][33] Phase I studies may be more susceptible.[34] Studies sponsored by industry are more likely to be positive.[35][36]

It is not simple to get a study published in any peer-reviewed journal, least of all in the best journals. Accordingly, many studies go unreported. It is often thought to be difficult to publish small studies, the outcome of which conflicts with the reported outcomes of larger previously published studies, or to publish studies from which no clear conclusion can be drawn. In part, this reflects the wish of the best journals to publish influential papers, and in part it reflects authors choosing not to publish studies that are thought to be uninteresting. Such publication bias can be difficult to recognise, but its effects tend to encourage publication of studies that support an already formed conclusion, while discouraging publication of contradictory or equivocal findings.[2][31]

## Related biases[edit]

### Language bias[edit]

Language bias may affect the results of meta-analyses.[37]

### Availability of full text on the Internet[edit]

e-publication bias

Stuides sponsored by industry may be more likely to be published with open access by journals with hybrid publication models.[38]

Full Text On the Net (FUTON) bias

Full Text On the Net (FUTON) bias may affect results of information retrieval.[39]

### No abstract available (NAA) bias[edit]

Certain knowledge domains may be more susceptible to 'no abstract available' (NAA) bias.[39]

### Selective outcome reporting bias[edit]

Among published articles, analyses of outcomes reported to be studied in unpublished protocols[40][16], FDA submissions[41], trial registration[42], or the methods sections of published papers[43] compared to the outcomes actually reported in the results of published papers found that outcomes with significant p-values are more likely to be reported, and reported sufficiently to allow inclusion in meta-analysis, than insignificant outcomes.

Selective outcome reporting bias may cause results of meta-analyses to be exaggerated.[44]

## Impact of publication bias[edit]

### Impact on meta-analysis[edit]

Publication bias is a major threat to the validity of meta-analysis. Publication bias against negative studies may threaten the validity of meta-analyses that are positive and all the studies included within the meta-analysis are small.[45][26]

In performing a meta-analyses, a file drawer[25] or a funnel plot analysis[26][27] may help detect underlying publication bias among the studies in the meta-analysis.

Publication bias has also occurred in the publication of randomized controlled trials of antidepressants.[10]

### Impact on the drug approval process[edit]

Publication bias occurs in the data submitted to the United States of America Food and Drug Administration[46][47] and to the Swedish drug regulatory authority[32]by drug companies.

### Impact on media coverage of scientific research[edit]

In journalism, the media is more likely to cover studies that report positive results.[48]

## Prevention[edit]

### Trial registration[edit]

In 2004, the International Committee of Medical Journal Editors (ICMJE) announced that all trials starting enrollment after July 1, 2005 must be registered prior to consideration for publication in one of the 12 member journals of the Committee.[49] Randomized controlled trials may be registered at sites such as http://controlled-trials.com/, http://isrctn.org, and http://clinicaltrials.gov.

## References[edit]

1. ↑ Anonymous (2025), Publication bias (English). Medical Subject Headings. U.S. National Library of Medicine.
2. ↑ 2.0 2.1 2.2 Dickersin K, Min YI, Meinert CL (1992). "Factors influencing publication of research results. Follow-up of applications submitted to two institutional review boards". JAMA 267 (3): 374–8. PMID 1727960. [e]
3. ↑ Nüesch E, Trelle S, Reichenbach S, Rutjes AW, Tschannen B, Altman DG et al. (2010). "Small study effects in meta-analyses of osteoarthritis trials: meta-epidemiological study.". BMJ 341: c3515. DOI:10.1136/bmj.c3515. PMID 20639294. PMC PMC2905513. Research Blogging.
4. ↑ Sterne JA, Egger M, Smith GD (2001). "Systematic reviews in health care: Investigating and dealing with publication and other biases in meta-analysis.". BMJ 323 (7304): 101-5. PMID 11451790. PMC PMC1120714.
5. ↑ F. Richy, O. Ethgen, O. Bruyere, F. Deceulaer & J. Reginster : From Sample Size to Effect-Size: Small Study Effect Investigation (SSEi) . The Internet Journal of Epidemiology. 2004 Volume 1 Number 2
6. ↑ McAlindon TE, LaValley MP, Gulin JP, Felson DT (2000). "Glucosamine and chondroitin for treatment of osteoarthritis: a systematic quality assessment and meta-analysis". JAMA 283 (11): 1469–75. PMID 10732937. [e]
7. ↑ Clegg DO, Reda DJ, Harris CL, et al (2006). "Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis". N. Engl. J. Med. 354 (8): 795–808. DOI:10.1056/NEJMoa052771. PMID 16495392. Research Blogging.
8. ↑ Vlad SC, LaValley MP, McAlindon TE, Felson DT (2007). "Glucosamine for pain in osteoarthritis: why do trial results differ?". Arthritis Rheum. 56 (7): 2267–77. DOI:10.1002/art.22728. PMID 17599746. Research Blogging.
9. ↑ Reichenbach S, Sterchi R, Scherer M, et al (2007). "Meta-analysis: chondroitin for osteoarthritis of the knee or hip". Ann. Intern. Med. 146 (8): 580–90. PMID 17438317. [e]
10. ↑ 10.0 10.1 Turner EH, Matthews AM, Linardatos E, Tell RA, Rosenthal R (2008). "Selective publication of antidepressant trials and its influence on apparent efficacy". N. Engl. J. Med. 358 (3): 252–60. DOI:10.1056/NEJMsa065779. PMID 18199864. Research Blogging.
11. ↑ Bourgeois FT, Murthy S, Mandl KD (2010). "Outcome reporting among drug trials registered in ClinicalTrials.gov.". Ann Intern Med 153 (3): 158-66. DOI:10.1059/0003-4819-153-3-201008030-00006. PMID 20679560. Research Blogging.
12. ↑ Jefferson T et al. Ensuring safe and effective drugs: who can do what it takes?. BMJ 2011; 342:c7258 DOI:10.1136/bmj.c7258 10.1136/bmj.c7258
13. ↑ Turner, Erick H.; Daniel Knoepflmacher, Lee Shapley (2012-03-20). "Publication Bias in Antipsychotic Trials: An Analysis of Efficacy Comparing the Published Literature to the US Food and Drug Administration Database". PLoS Med 9 (3): e1001189. DOI:10.1371/journal.pmed.1001189. Retrieved on 2012-03-21. Research Blogging.
14. ↑ Eyding D, Lelgemann M, Grouven U, Härter M, Kromp M, Kaiser T et al. (2010). "Reboxetine for acute treatment of major depression: systematic review and meta-analysis of published and unpublished placebo and selective serotonin reuptake inhibitor controlled trials.". BMJ 341: c4737. DOI:10.1136/bmj.c4737. PMID 20940209. Research Blogging.
15. ↑ Decullier E, Lhéritier V, Chapuis F (2005). "Fate of biomedical research protocols and publication bias in France: retrospective cohort study.". BMJ 331 (7507): 19. DOI:10.1136/bmj.38488.385995.8F. PMID 15967761. PMC PMC558532. Research Blogging.
16. ↑ 16.0 16.1 Chan AW, Krleza-Jerić K, Schmid I, Altman DG (2004). "Outcome reporting bias in randomized trials funded by the Canadian Institutes of Health Research.". CMAJ 171 (7): 735-40. DOI:10.1503/cmaj.1041086. PMID 15451835. PMC PMC517858. Research Blogging.
17. ↑ 17.0 17.1 Pham B, Klassen TP, Lawson ML, Moher D (2005). "Language of publication restrictions in systematic reviews gave different results depending on whether the intervention was conventional or complementary". J Clin Epidemiol 58 (8): 769–76. PMID 16086467. [e]
18. ↑ Galandi D, Schwarzer G, Antes G (2006). "The demise of the randomised controlled trial: bibliometric study of the German-language health care literature, 1948 to 2004". BMC Med Res Methodol 6: 30. DOI:10.1186/1471-2288-6-30. PMID 16824217. Research Blogging.
19. ↑ Lancet. 1997. Language bias in randomised controlled trials published in English and German. http://pubmed.gov/16086467
20. ↑ Scherer RW, Langenberg P, von Elm E (2007). "Full publication of results initially presented in abstracts.". Cochrane Database Syst Rev (2): MR000005. DOI:10.1002/14651858.MR000005.pub3. PMID 17443628. Research Blogging.
21. ↑ Scherer RW, Dickersin K, Langenberg P (1994). "Full publication of results initially presented in abstracts. A meta-analysis.". JAMA 272 (2): 158-62. PMID 8015133.
22. ↑ Hopewell S, Clarke M, Stewart L, Tierney J (2007). "Time to publication for results of clinical trials.". Cochrane Database Syst Rev (2): MR000011. DOI:10.1002/14651858.MR000011.pub2. PMID 17443632. Research Blogging.
23. ↑ Owens DK, Holodniy M, Garber AM, et al (May 1996). "Polymerase chain reaction for the diagnosis of HIV infection in adults. A meta-analysis with recommendations for clinical practice and study design". Ann. Intern. Med. 124 (9): 803–15. PMID 8610949. [e]
24. ↑ Irwig L, Macaskill P, Glasziou P, Fahey M (January 1995). "Meta-analytic methods for diagnostic test accuracy". J Clin Epidemiol 48 (1): 119–30; discussion 131–2. PMID 7853038. [e]
25. ↑ 25.0 25.1 Pham B et al. (2001). "Is there a "best" way to detect and minimize publication bias? An empirical evaluation". Evaluation & the Health Professions 24: 109–25. PMID 11523382. [e]
26. ↑ 26.0 26.1 26.2 Egger M et al. (1997). "Bias in meta-analysis detected by a simple, graphical test". BMJ 315: 629–34. PMID 9310563. PMC PMC2127453. [e]
27. ↑ 27.0 27.1 27.2 Terrin N, Schmid CH, Lau J (2005). "In an empirical evaluation of the funnel plot, researchers could not visually identify publication bias.". J Clin Epidemiol 58 (9): 894-901. DOI:10.1016/j.jclinepi.2005.01.006. PMID 16085192. Research Blogging.
28. ↑ Moreno, Santiago G; Alex J Sutton, Erick H Turner, Keith R Abrams, Nicola J Cooper, Tom M Palmer, A E Ades (2009-08-07). "Novel methods to deal with publication biases: secondary analysis of antidepressant trials in the FDA trial registry database and related journal publications". BMJ 339 (aug07_1): b2981. DOI:10.1136/bmj.b2981. Retrieved on 2009-08-13. Research Blogging.
29. ↑ Tang JL, Liu JL (2000). "Misleading funnel plot for detection of bias in meta-analysis.". J Clin Epidemiol 53 (5): 477-84. PMID 10812319. [e]
30. ↑ Deeks JJ, Macaskill P, Irwig L (September 2005). "The performance of tests of publication bias and other sample size effects in systematic reviews of diagnostic test accuracy was assessed". J Clin Epidemiol 58 (9): 882–93. DOI:10.1016/j.jclinepi.2005.01.016. PMID 16085191. Research Blogging.
31. ↑ 31.0 31.1 31.2 Krzyzanowska MK et al. (2003). "Factors associated with failure to publish large randomized trials presented at an oncology meeting". JAMA 290: 495–501. DOI:10.1001/jama.290.4.495. PMID 12876092. Research Blogging.
32. ↑ 32.0 32.1 Melander H, Ahlqvist-Rastad J, Meijer G, Beermann B (2003). "Evidence b(i)ased medicine--selective reporting from studies sponsored by pharmaceutical industry: review of studies in new drug applications". BMJ 326 (7400): 1171–3. DOI:10.1136/bmj.326.7400.1171. PMID 12775615. Research Blogging.
33. ↑ Lexchin J et al. (2003). "Pharmaceutical industry sponsorship and research outcome and quality: systematic review". BMJ 326: 1167–70. DOI:10.1136/bmj.326.7400.1167. PMID 12775614. Research Blogging.
34. ↑ Decullier, Evelyne; An-Wen Chan, François Chapuis (2009-02-01). "Inadequate Dissemination of Phase I Trials: A Retrospective Cohort Study". PLoS Medicine 6 (2): e34 EP -. DOI:10.1371/journal.pmed.1000034. Retrieved on 2009-02-19. Research Blogging.
35. ↑ Djulbegovic B, Lacevic M, Cantor A, Fields KK, Bennett CL, Adams JR, Kuderer NM, Lyman GH. The uncertainty principle and industry-sponsored research. Lancet. 2000 Aug 19;356(9230):635-8. PMID 10968436
36. ↑ Rochon PA, Gurwitz JH, Simms RW, Fortin PR, Felson DT, Minaker KL, Chalmers TC. A study of manufacturer-supported trials of nonsteroidal anti-inflammatory drugs in the treatment of arthritis. Arch Intern Med. 1994 Jan 24;154(2):157-63. PMID 8285810
37. ↑ Grégoire G, Derderian F, Le Lorier J (January 1995). "Selecting the language of the publications included in a meta-analysis: is there a Tower of Babel bias?". J Clin Epidemiol 48 (1): 159–63. PMID 7853041. [e]
38. ↑ Jakobsen AK, Christensen R, Persson R, Bartels EM, Kristensen LE (2010). "And now, e-publication bias.". BMJ 340: c2243. DOI:10.1136/bmj.c2243. PMID 20427450. Research Blogging.
39. ↑ 39.0 39.1 Wentz R (October 2002). "Visibility of research: FUTON bias". Lancet 360 (9341): 1256. DOI:10.1016/S0140-6736(02)11264-5. PMID 12401287. Research Blogging.
40. ↑ Chan AW, Hróbjartsson A, Haahr MT, Gøtzsche PC, Altman DG (2004). "Empirical evidence for selective reporting of outcomes in randomized trials: comparison of protocols to published articles.". JAMA 291 (20): 2457-65. DOI:10.1001/jama.291.20.2457. PMID 15161896. Research Blogging.
41. ↑ Rising K, Bacchetti P, Bero L (2008). "Reporting bias in drug trials submitted to the Food and Drug Administration: review of publication and presentation.". PLoS Med 5 (11): e217; discussion e217. DOI:10.1371/journal.pmed.0050217. PMID 19067477. PMC PMC2586350. Research Blogging.
42. ↑ Mathieu, Sylvain; Isabelle Boutron, David Moher, Douglas G. Altman, Philippe Ravaud (2009-09-02). "Comparison of Registered and Published Primary Outcomes in Randomized Controlled Trials". JAMA 302 (9): 977-984. DOI:10.1001/jama.2009.1242. Retrieved on 2009-09-01. Research Blogging.
43. ↑ Chan AW, Altman DG (April 2005). "Identifying outcome reporting bias in randomised trials on PubMed: review of publications and survey of authors". BMJ 330 (7494): 753. DOI:10.1136/bmj.38356.424606.8F. PMID 15681569. PMC 555875. Research Blogging.
44. ↑ Kirkham JJ, Dwan KM, Altman DG, Gamble C, Dodd S, Smyth R et al. (2010). "The impact of outcome reporting bias in randomised controlled trials on a cohort of systematic reviews.". BMJ 340: c365. DOI:10.1136/bmj.c365. PMID 20156912. Research Blogging.
45. ↑ Sutton AJ, Duval SJ, Tweedie RL, Abrams KR, Jones DR (2000). "Empirical assessment of effect of publication bias on meta-analyses". BMJ 320 (7249): 1574–7. PMID 10845965. [e]
46. ↑ Lee K, Bacchetti P, Sim I. Publication of Clinical Trials Supporting Successful New Drug Applications: A Literature Analysis. PLoS Medicine. 2008 Sep 1;5(9):e191 EP -. DOI:10.1371/journal.pmed.0050191
47. ↑ Rising, Kristin; Peter Bacchetti, Lisa Bero (2008-11-01). "Reporting Bias in Drug Trials Submitted to the Food and Drug Administration: Review of Publication and Presentation". PLoS Medicine 5 (11): e217 EP -. DOI:10.1371/journal.pmed.0050217. Retrieved on 2008-11-26. Research Blogging.
48. ↑ Koren G, Klein N (October 1991). "Bias against negative studies in newspaper reports of medical research". JAMA 266 (13): 1824–6. PMID 1890712. [e]
49. ↑ De Angelis C, Drazen JM, Frizelle FA, et al (September 2004). "Clinical trial registration: a statement from the International Committee of Medical Journal Editors". The New England journal of medicine 351 (12): 1250–1. DOI:10.1056/NEJMe048225. PMID 15356289. Research Blogging.