Turning a blind eye: the success of blinding reported in a random sample of randomised, placebo controlled trials

doi:10.1136/bmj.37952.631667.EE

BMJ, doi: 10.1136/bmj.37952.631667.EE, (Published 22 January 2004)

PAPERS

Turning a blind eye: the success of blinding reported in a random sample of randomised, placebo controlled trials

Dean Fergusson ¹, Kathleen Cranley Glass ², Duff Waring ³, Stan Shapiro ⁴

¹ Ottawa Health Research Institute, Clinical Epidemiology Program, 501 Smyth Road, Box 201, Ottawa, ON, Canada K1H 8L6
² Departments of Human Genetics & Pediatrics and Biomedical Ethics Unit, McGill University, Montreal, QC, Canada
³ Research Ethics and Regulation Group, Faculty of Law, University of Toronto, Toronto, ON, Canada
⁴ Department of Epidemiology and Biostatistics, McGill University

Objective To examine the reporting and success of double blindingin a sample of randomised, placebo controlled trials from leadinggeneral medicine and psychiatry journals.

Methods Identificationof placebo controlled, randomised controlled trials from prespecifiedgeneral medical and psychiatric journals indexed on Medlinebetween 1 January 1998 and 1 October 2001, from which a randomsample of 200 randomised clinical trials was chosen, of which191 trials were evaluated.

Results Only seven of the 97 (7%)general medicine trials provided evidence on the success ofblinding, with five reporting that the success of blinding wasimperfect. In trials from psychiatric journals, the successof blinding was reported in eight of the 94 trials, with fourreporting that the blinding was imperfect. Overall, only fourof the 191 (2%) trials assessed blinding in the participantsand either the outcome assessors or the investigators.

ConclusionsThe current lack of reporting on the success of blinding provideslittle evidence that success of blinding is maintained in placebocontrolled trials. Trialists and editors should make a concertedeffort to incorporate, report, and publish such informationand its potential effect on study results.

(Accepted 11 November 2003)

CiteULike

Complore

Connotea

Del.icio.us Add to Digg

Digg

StumbleUpon Add to Technorati

Technorati What's this?

Relevant Articles

Future of psychotherapy in the NHS: Control groups play important part: D B Double
BMJ 2004 329: 514. [Extract] [Full Text]

Turning a blind eye: Testing the success of blinding and the CONSORT statement: Douglas G Altman, Kenneth F Schulz, and David Moher
BMJ 2004 328: 1135. [Extract] [Full Text]

Turning a blind eye: Authors have blinkered view of blinding: Stephen J Senn
BMJ 2004 328: 1135-1136. [Extract] [Full Text]

Turning a blind eye: Why we don't test for blindness at the end of our trials: David L Sackett
BMJ 2004 328: 1136. [Extract] [Full Text]

Evidence of success of blinding in clinical trials is scant
BMJ 2004 328: 0. [Full Text]

This article has been cited by other articles:

Howick, J., Glasziou, P., Aronson, J. K (2009). The evolution of evidence hierarchies: what can Bradford Hill's 'guidelines for causation' contribute?. JRSM 102: 186-194 [Full text]
Filion, K. B. MSc, Belisle, P. MSc, Joseph, L. PhD, Paradis, G. MD MSc, Rinfret, S. MD MSc, Eisenberg, M. J. MD MPH (2008). Smoking cessation trials. CMAJ 179: 1038-1038 [Full text]
Sackett, D. L (2007). Commentary: Measuring the success of blinding in RCTs: don't, must, can't or needn't?. Int J Epidemiol 36: 664-665 [Full text]
Hrobjartsson, A, Forfang, E, Haahr, M., Als-Nielsen, B, Brorson, S (2007). Blinded trials taken to the test: an analysis of randomized clinical trials that report tests for the success of blinding. Int J Epidemiol 36: 654-663 [Abstract] [Full text]
Poolman, R. W., Struijs, P. A.A., Krips, R., Sierevelt, I. N., Marti, R. K., Farrokhyar, F., Bhandari, M. (2007). Reporting of Outcomes in Orthopaedic Randomized Trials: Does Blinding of Outcome Assessors Matter?. JBJS 89: 550-558 [Abstract] [Full text]
Vickrey, B. G., Mittman, B. S., Connor, K. I., Pearson, M. L., Della Penna, R. D., Ganiats, T. G., DeMonte, R. W. Jr., Chodosh, J., Cui, X., Vassar, S., Duan, N., Lee, M. (2006). The Effect of a Disease Management Intervention on Quality and Outcomes of Dementia Care: A Randomized, Controlled Trial.. ANN INTERN MED 145: 713-726 [Abstract] [Full text]
Bausell, R. B., Lao, L., Bergman, S., Lee, W.-L., Berman, B. M. (2005). Is Acupuncture Analgesia an Expectancy Effect?: Preliminary Evidence Based on Participants' Perceived Assignments in Two Placebo-Controlled Trials. Eval Health Prof 28: 9-26 [Abstract]
Matthews, S B, Waud, J P, Roberts, A G, Campbell, A K (2005). Systemic lactose intolerance: a new perspective on an old problem. Postgrad. Med. J. 81: 167-173 [Abstract] [Full text]
Double, D B (2004). Future of psychotherapy in the NHS: Control groups play important part. BMJ 329: 514-514 [Full text]
Altman, D. G, Schulz, K. F, Moher, D. (2004). Turning a blind eye: Testing the success of blinding and the CONSORT statement. BMJ 328: 1135-1135 [Full text]
Senn, S. J (2004). Turning a blind eye: Authors have blinkered view of blinding. BMJ 328: 1135-1136 [Full text]
Sackett, D. L (2004). Turning a blind eye: Why we don't test for blindness at the end of our trials. BMJ 328: 1136-1136 [Full text]

Rapid Responses:

Read all Rapid Responses

A Blinkered view of Blinding: Stephen J Senn
bmj.com, 20 Feb 2004 [Full text]
Why we don't test for blindness at the end of our trials.: David L. Sackett
bmj.com, 20 Feb 2004 [Full text]
Changing the mindset about unblinding in clinical trials: D B Double
bmj.com, 21 Feb 2004 [Full text]
Testing the success of blinding and the CONSORT Statement: Douglas G. Altman, et al.
bmj.com, 21 Feb 2004 [Full text]
The Blind leading the Blind?: Michael Goodyear
bmj.com, 24 Feb 2004 [Full text]
Widening the field of vision: Stan Shapiro, et al.
bmj.com, 24 Feb 2004 [Full text]
Turning a blind eye to bias in clinical trials: D B Double
bmj.com, 26 Feb 2004 [Full text]
Blind evaluation of blinding process: Santosh K Chaturvedi
bmj.com, 2 Mar 2004 [Full text]
Failure to assess blinding can make clinical trials hard to interpret: Andrei SP Brennan, et al.
bmj.com, 23 Mar 2004 [Full text]
The Paradox of the Placebo: Raywat S. Deonandan, et al.
bmj.com, 16 Jun 2004 [Full text]
Placebo-controlled: is it really a MeSH term?: Jafar Kolahi
bmj.com, 29 Sep 2006 [Full text]