Contamination in trials: is cluster randomisation the answer?

doi:10.1136/bmj.322.7282.355

BMJ 2001;322:355-357 ( 10 February )

Education and debate

Contamination in trials: is cluster randomisation the answer?

David J Torgerson, senior research fellow.

Centre for Health Economics, University of York, York YO10 5DD

djt6@york.ac.uk

The first 150 words of the full text of this article appear below.

Most randomised trials allocate individual participants to different treatments. However, cluster randomised trials in whichgroups of subjects are allocated to different treatments are becomingincreasingly popular.¹ Cluster randomisation is often advocatedto minimise treatment "contamination" between intervention andcontrol participants. For example, in a trial of dietary change,people in the control group might learn about the experimentaldiet and adopt itthemselves.

Contamination of control participants has two related effects. It reduces the point estimate of an intervention's effectivenessand this apparent reduction may lead to a type II error $---$ that is,rejection of an effective intervention as ineffective becausethe observed effect size was neither statistically nor clinicallysignificant.

Although the threat of contamination is an issue in some controlled trials, it may be not be of much practical importancein many. Trialists should use individual randomisation if possiblebecause of the drawbacks of cluster allocation. Cluster . . . [Full text of this article]

CiteULike

Complore

Connotea

Del.icio.us Add to Digg

Digg

StumbleUpon Add to Technorati

Technorati What's this?

Relevant Articles

Effects of algorithm for diagnosis of active labour: cluster randomised trial: Helen Cheyne, Vanora Hundley, Dawn Dowding, J Martin Bland, Paul McNamee, Ian Greer, Maggie Styles, Carol A Barnett, Graham Scotland, and Catherine Niven
BMJ 2008 337: a2396. [Abstract] [Full Text] [PDF]

Evaluation of Talking Parents, Healthy Teens, a new worksite based parenting programme to promote parent-adolescent communication about sexual health: randomised controlled trial: Mark A Schuster, Rosalie Corona, Marc N Elliott, David E Kanouse, Karen L Eastman, Annie J Zhou, and David J Klein
BMJ 2008 337: a308. [Abstract] [Full Text] [PDF]

Selection bias in cluster trial: David J Torgerson
BMJ 2008 336: 573. [Extract] [Full Text] [PDF]

This article has been cited by other articles:

Jackson, J., Mandel, D., Blanchard, J., Carlson, M., Cherry, B., Azen, S., Chou, C.-P., Jordan-Marsh, M., Forman, T., White, B., Granger, D., Knight, B., Clark, F. (2009). Confronting challenges in intervention research with ethnically diverse older adults: the USC Well Elderly II Trial. Clin Trials 6: 90-101 [Abstract]
Cheyne, H., Hundley, V., Dowding, D., Bland, J M., McNamee, P., Greer, I., Styles, M., Barnett, C. A, Scotland, G., Niven, C. (2008). Effects of algorithm for diagnosis of active labour: cluster randomised trial. BMJ 337: a2396-a2396 [Abstract] [Full text]
Shcherbatykh, I., Holbrook, A., Thabane, L., Dolovich, L., COMPETE III investigators, (2008). Methodologic Issues in Health Informatics Trials: The Complexities of Complex Interventions. J. Am. Med. Inform. Assoc. 15: 575-580 [Abstract] [Full text]
Schuster, M. A, Corona, R., Elliott, M. N, Kanouse, D. E, Eastman, K. L, Zhou, A. J, Klein, D. J (2008). Evaluation of Talking Parents, Healthy Teens, a new worksite based parenting programme to promote parent-adolescent communication about sexual health: randomised controlled trial. BMJ 337: a308-a308 [Abstract] [Full text]
Zimmermann, C., Riechelmann, R., Krzyzanowska, M., Rodin, G., Tannock, I. (2008). Effectiveness of Specialized Palliative Care: A Systematic Review. JAMA 299: 1698-1709 [Abstract] [Full text]
Torgerson, D. J (2008). Selection bias in cluster trial. BMJ 336: 573-573 [Full text]
Melis, R. J. F., van Eijken, M. I. J., Teerenstra, S., van Achterberg, T., Parker, S. G., Borm, G. F., van de Lisdonk, E. H., Wensing, M., Rikkert, M. G. M. O. (2008). Multidimensional Geriatric Assessment: Back to the Future A Randomized Study of a Multidisciplinary Program to Intervene on Geriatric Syndromes in Vulnerable Older People Who Live at Home (Dutch EASYcare Study). Journals of Gerontology Series A: Biological Sciences and Medical Sciences 63: 283-290 [Abstract] [Full text]
Morriss, R., Dowrick, C., Salmon, P., Peters, S., Dunn, G., Rogers, A., Lewis, B., Charles-Jones, H., Hogg, J., Clifford, R., Rigby, C., Gask, L. (2007). Cluster randomised controlled trial of training practices in reattribution for medically unexplained symptoms. Br. J. Psychiatry 191: 536-542 [Abstract] [Full text]
Shetty, A. (2007). Depression post-myocardial infarction. Br. J. Psychiatry 191: 455-456 [Full text]
Fowell, A, Johnstone, R, Finlay, I G, Russell, D, Russell, I T (2006). Design of trials with dying patients: a feasibility study of cluster randomisation versus randomised consent. Palliat Med 20: 799-804 [Abstract]
Roberts, C., Roberts, S. A (2005). Design and analysis of clinical trials with clustering effects due to treatment. Clin Trials 2: 152-162 [Abstract]
James, J., Thomas, P., Cavan, D., Kerr, D. (2004). Preventing childhood obesity by reducing consumption of carbonated drinks: cluster randomised controlled trial. BMJ 328: 1237- [Abstract] [Full text]
Donner, A., Klar, N. (2004). Pitfalls of and Controversies in Cluster Randomization Trials. AJPH 94: 416-422 [Abstract] [Full text]
Chuang, J.-H., Hripcsak, G., Heitjan, D. F. (2002). Design and Analysis of Controlled Trials in Naturally Clustered Environments: Implications for Medical Informatics. J. Am. Med. Inform. Assoc. 9: 230-238 [Abstract] [Full text]
Bonell, C, Imrie, J (2001). Behavioural interventions to prevent HIV infection: rapid evolution, increasing rigour, moderate success. Br Med Bull 58: 155-170 [Abstract] [Full text]
Chinn, S. (2001). Statistics for the European Respiratory Journal. Eur Respir J 18: 393-401 [Abstract] [Full text]
Steiner, A., Walsh, B., Pickering, R. M, Wiles, R., Ward, J., Brooking, J. I, Torgerson, D. J (2001). Therapeutic nursing or unblocking beds? A randomised controlled trial of a post-acute intermediate care unit Commentary: Problems with randomised consent Authors' reply. BMJ 322: 453-460 [Abstract] [Full text]