Access to clinical trial data
Abstract
Results and protocols go hand in hand The high frequency and negative impact of selective reporting of data from clinical trials are well documented.1 The widespread occurrence of data suppression means that healthcare practitioners and policy makers largely make decisions on the basis of an incomplete and biased subset of trial results. Selective reporting can often be identified by reviewing trial protocols and publications; it can be mitigated by defining standard core outcome sets for trials, and by ensuring access to all unpublished and published data⇓.2 3 However, two linked articles highlight major difficulties in obtaining access to protocols and unpublished data for both industry and non-industry trials and provide new insight into trialists’ reasons for suppressing data.4 5 These types of challenges have been described before,6 7 and they reinforce the core principle that full knowledge of both the methods and results for all trials, independent of publication status, is essential for a complete and unbiased evaluation of an intervention. Sources of information that should be consulted when appraising an intervention include trial protocols, registry records, regulatory agency documents, trial datasets, and journal publications. Smyth and colleagues (doi:10.1136/bmj.c7153) also show …
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Such bias can only be identified and deterred if trial outcomes are clearly defined a priori in the protocol, and if protocol information is made public.
“Such bias can only be identified and deterred if trial outcomes are clearly defined a priori in the protocol, and if protocol information is made public.78 260 261 262”
From SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials (2025) · cites this paper as [260]
Cites
Systematic Review of the Empirical Evidence of Study Publication Bias and Outcome Reporting Bias
Dwan, K., Altman, D. G., Arnaiz, J. A., Bloom, J., Chan, A.-W., Cronin, E., Decullier, E., Easterbrook, P. J., Von Elm, E., Gamble, C., et al. (2008) · PLoS ONE · doi:10.1371/journal.pone.0003081 · Cited by 1,546 · see citing works
Self-citationDissemination and publication of research findings: an updated review of related biases
Song, F., Parekh, Hooper, L., Loke, Y., Ryder, J., Sutton, A., Hing, C., Kwok, C., Pang, C., & Harvey, I. (2010) · Health Technology Assessment · doi:10.3310/hta14080 · Cited by 1,039 · see citing works
Frequency and reasons for outcome reporting bias in clinical trials: interviews with trialists
Smyth, R. M. D., Kirkham, J. J., Jacoby, A., Altman, D. G., Gamble, C., & Williamson, P. R. (2011) · BMJ · doi:10.1136/bmj.c7153 · Cited by 220 · see citing works
Moving Toward Transparency of Clinical Trials
Zarin, D. A., & Tse, T. (2008) · Science · doi:10.1126/science.1153632 · Cited by 183 · see citing works
Whose data set is it anyway? Sharing raw data from randomized trials
Vickers, A. J. (2006) · Trials · doi:10.1186/1745-6215-7-15 · Cited by 149 · see citing works
Bias, Spin, and Misreporting: Time for Full Access to Trial Protocols and Results
Chan, A.-W. (2008) · PLoS Medicine · doi:10.1371/journal.pmed.0050230 · Cited by 144 · see citing works
Self-citationHrynaszkiewicz, I., Norton, M. L., Vickers, A. J., & Altman, D. G. (2010) · Trials · doi:10.1186/1745-6215-11-9 · Cited by 128 · see citing works
Towards agreement on best practice for publishing raw clinical trial data
Hrynaszkiewicz, I., & Altman, D. G. (2009) · Trials · doi:10.1186/1745-6215-10-17 · Cited by 71 · see citing works
Waiving confidentiality for the greater good
Chan, A., Upshur, R. E. G., Singh, J. A., Ghersi, D., Chapuis, F. R., & Altman, D. G. (2006) · BMJ · doi:10.1136/bmj.332.7549.1086 · Cited by 46 · see citing works
Self-citationEnsuring safe and effective drugs: who can do what it takes?
Jefferson, T., Doshi, P., Thompson, M., Heneghan, C. J., & C. A. R. I. Group (2011) · BMJ · doi:10.1136/bmj.c7258 · Cited by 43 · see citing works
Finding studies on reboxetine: a tale of hide and seek
Wieseler, B., McGauran, N., & Kaiser, T. (2010) · BMJ · doi:10.1136/bmj.c4942 · Cited by 36 · see citing works
Strengthening the credibility of clinical research
DeAngelis, C. D., & Fontanarosa, P. (2010) · The Lancet · doi:10.1016/s0140-6736(10)61145-2 · Cited by 24 · see citing works
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SPIRIT 2013 Statement: Defining Standard Protocol Items for Clinical Trials
Chan, A.-W., Tetzlaff, J. M., Altman, D. G., Laupacis, A., Gøtzsche, P. C., Krleža-Jerić, K., Hróbjartsson, A., Mann, H., Dickersin, K., Berlin, J. A., et al. (2013) · Annals of Internal Medicine · doi:10.7326/0003-4819-158-3-201302050-00583 · Cited by 7,363 · see citing works
Self-citationSPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials
Chan, A.-W., Tetzlaff, J. M., Gotzsche, P. C., Altman, D. G., Mann, H., Berlin, J. A., Dickersin, K., Hrobjartsson, A., Schulz, K. F., Parulekar, W. R., et al. (2013) · BMJ · doi:10.1136/bmj.e7586 · Cited by 6,251 · see citing works
Self-citationIncreasing value and reducing waste: addressing inaccessible research
Chan, A.-W., Song, F., Vickers, A., Jefferson, T., Dickersin, K., Gøtzsche, P. C., Krumholz, H. M., Ghersi, D., & van der Worp, H. B. (2014) · The Lancet · doi:10.1016/s0140-6736(13)62296-5 · Cited by 887 · see citing works
Self-citationPreparing for Responsible Sharing of Clinical Trial Data
Mello, M. M., Francer, J. K., Wilenzick, M., Teden, P., Bierer, B. E., & Barnes, M. (2013) · New England Journal of Medicine · doi:10.1056/nejmhle1309073 · Cited by 175 · see citing works
SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials
Hróbjartsson, A., Boutron, I., Hopewell, S., Moher, D., Schulz, K. F., Collins, G. S., Tunn, R., Aggarwal, R., Berkwits, M., Berlin, J. A., et al. (2025) · BMJ · doi:10.1136/bmj-2024-081660 · Cited by 171 · see citing works
Self-citationOut of sight but not out of mind: how to search for unpublished clinical trial evidence
Chan, A.-W. (2012) · BMJ · doi:10.1136/bmj.d8013 · Cited by 62 · see citing works
Self-citationResearch accomplishments that are too good to be true
Ioannidis, J. P. A. (2014) · Intensive Care Medicine · doi:10.1007/s00134-013-3100-z · Cited by 12 · see citing works
Completeness of clinical evidence citation in trial protocols: A cross-sectional analysis
Sheng, J., Feldhake, E., Zarin, D. A., & Kimmelman, J. (2022) · Med · doi:10.1016/j.medj.2022.03.002 · Cited by 7 · see citing works
- Authors
- Chan, A.-W.
- Affiliations
- University of Toronto (CA)
- Corresponding author
- Chan, A.-W.
- Venue
- BMJ
- Publisher
- BMJ
- Published
- 2011-01-12
- Volume
- 342
- Issue
- jan12 2
- Pages
- d80-d80
- ISSN
- 0007-1447 (ISSN-L)
- 0959-8138
- 1468-5833
- OpenAlex
- W2066235415
- Cited by
- 27
- References
- 12
- Citations by year
- 2025: 1 · 2022: 1 · 2021: 1 · 2020: 2 · 2016: 1 · 2015: 3 · 2014: 4 · 2013: 5 · 2012: 3
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- BMJ (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmaceutical industry and healthcare
- Physical Sciences › Computer Science › Information Systems › Research Data Management Practices
- Keywords
- clinical trial data access, selective reporting, data suppression, unpublished data, core outcome set, industry-sponsored trials, clinical trial registries, research integrity
- MeSH terms
- Clinical Trials as Topic, Information Dissemination
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