Allocation techniques for balance at baseline in cluster randomized trials: a methodological review

Trials

Merrick Zwarenstein³  Ross Upshur¹  Karen Tu⁴  Baiju R Shah¹  Jeremy M Grimshaw⁵  Jan Barnsley²  Ilana J Halperin⁶  Noah M Ivers² 

[1] Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3 M5, Canada;Institute of Health Policy Management and Evaluation, University of Toronto, Health Sciences Building, 155 College Street, Suite 425, Toronto, ON, M5T3M6, Canada;Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue, Toronto, ON, M4N3M5, Canada;Toronto Western Hospital Family Health Team, University Health Network, 399 Bathurst Street, West Wing, 2nd Floor, Toronto, ON, M5T2S8, Canada;Clinical Epidemiology Program, Ottawa Health Research Institute, 1053 Carling Avenue, Administration Building, Room 2-017, Ottawa, ON, K1Y 4E9, Canada;Division of Endocrinology and Metabolism, Department of Medicine, University of Toronto, 200 Elizabeth St, EN12-218, Toronto, ON, M5G2C4, Canada

关键词: Restricted randomization;    Balanced allocation;    Cluster-randomized trials;   

Others  :  1095441
DOI  :  10.1186/1745-6215-13-120

 received in 2011-12-23, accepted in 2012-07-09,  发布年份 2012

【 摘 要 】

Reviews have repeatedly noted important methodological issues in the conduct and reporting of cluster randomized controlled trials (C-RCTs). These reviews usually focus on whether the intracluster correlation was explicitly considered in the design and analysis of the C-RCT. However, another important aspect requiring special attention in C-RCTs is the risk for imbalance of covariates at baseline. Imbalance of important covariates at baseline decreases statistical power and precision of the results. Imbalance also reduces face validity and credibility of the trial results. The risk of imbalance is elevated in C-RCTs compared to trials randomizing individuals because of the difficulties in recruiting clusters and the nested nature of correlated patient-level data. A variety of restricted randomization methods have been proposed as way to minimize risk of imbalance. However, there is little guidance regarding how to best restrict randomization for any given C-RCT. The advantages and limitations of different allocation techniques, including stratification, matching, minimization, and covariate-constrained randomization are reviewed as they pertain to C-RCTs to provide investigators with guidance for choosing the best allocation technique for their trial.

【 授权许可】

   
2012 Ivers et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1 .

【 参考文献 】

• [1]Donner A, Klar N: Design and Analysis of Cluster Randomization Trials in Health Research. New York, NY: Oxford University Press; 2000.
• [2]Murray DM, Pals SL, Blitstein JL, Alfano CM, Lehman J: Design and analysis of group-randomized trials in cancer: a review of current practices. J Natl Cancer Inst 2008, 100:483-491.
• [3]Varnell SP, Murray DM, Janega JB, Blitstein JL: Design and analysis of group-randomized trials: a review of recent practices. Am J Public Health 2004, 94:393-399.
• [4]Ivers NM, Taljaard M, Dixon S, Bennett C, McRae A, Taleban J, Skea Z, Brehaut JC, Boruch RF, Eccles MP, Grimshaw JM, Weijer C, Zwarenstein M, Donner A: Impact of CONSORT extension for cluster randomised trials on quality of reporting and study methodology: review of random sample of 300 trials, 2000–8. BMJ 2011, 343:d5886.
• [5]Eldridge SM, Ashby D, Feder GS, Rudnicka AR, Ukoumunne OC: Lessons for cluster randomized trials in the twenty-first century: a systematic review of trials in primary care. Clin Trials 2004, 1:80-90.
• [6]Eldridge S, Ashby D, Bennett C, Wakelin M, Feder G: Internal and external validity of cluster randomised trials: systematic review of recent trials. BMJ 2008, 336:876-880.
• [7]Campbell MK, Elbourne DR, Altman DG: CONSORT group: CONSORT statement: extension to cluster randomised trials. BMJ 2004, 328:702-708.
• [8]Rosenberger WF: Randomization in clinical trials. New York, NY: Wiley; 2002.
• [9]Kalish LA, Begg CB: Treatment allocation methods in clinical trials: A review. Statist Med 1985, 4:129-144.
• [10]Atkinson AC: The comparison of designs for sequential clinical trials with covariate information. Journal of the Royal Statistical Society: Series A (Statistics in Society) 2002, 165:349-373.
• [11]Heritier S, Gebski V, Pillai A: Dynamic balancing randomization in controlled clinical trials. Stat Med 2005, 24:3729-3741.
• [12]Roozenbeek B, Maas AI, Lingsma HF, Butcher I, Lu J, Marmarou A, McHugh GS, Weir J, Murray GD, Steyerberg EW: IMPACT Study Group: Baseline characteristics and statistical power in randomized controlled trials: selection, prognostic targeting, or covariate adjustment? Crit Care Med 2009, 37:2683-2690.
• [13]Senn S: Testing for baseline balance in clinical trials. Stat Med 1994, 13:1715-1726.
• [14]Flynn TN, Whitley E, Peters TJ: Recruitment strategies in a cluster randomized trial-cost implications. Stat Med 2002, 21:397-405.
• [15]Carter B: Cluster size variability and imbalance in cluster randomized controlled trials. Stat Med 2010, 29:2984-2993.
• [16]Kerry SM, Bland JM: Unequal cluster sizes for trials in English and Welsh general practice: implications for sample size calculations. Stat Med 2001, 20:377-390.
• [17]Guittet L, Ravaud P, Giraudeau B: Planning a cluster randomized trial with unequal cluster sizes: practical issues involving continuous outcomes. BMC Med Res Methodol 2006, 6:17. BioMed Central Full Text
• [18]Gattellari M, Leung DY, Ukoumunne OC, Zwar N, Grimshaw J, Worthington JM: Study protocol: the DESPATCH study: Delivering stroke prevention for patients with atrial fibrillation - a cluster randomised controlled trial in primary healthcare. Implement Sci 2011, 6:48. BioMed Central Full Text
• [19]Kerry SM, Cappuccio FP, Emmett L, Plange-Rhule J, Eastwood JB: Reducing selection bias in a cluster randomized trial in West African villages. Clin Trials 2005, 2:125-129.
• [20]Raab GM, Butcher I: Balance in cluster randomized trials. Stat Med 2001, 20:351-365.
• [21]Altman DG, Dore CJ: Randomisation and baseline comparisons in clinical trials. Lancet 1990, 335:149-153.
• [22]Donner A, Klar N: Methods for comparing event rates in intervention studies when the unit of allocation is a cluster. Am J Epidemiol 1994, 140:279-289. discussion 300–301
• [23]Solomon DH, Polinski JM, Stedman M, Truppo C, Breiner L, Egan C, Jan S, Patel M, Weiss TW, Chen YT, Brookhart MA: Improving care of patients at-risk for osteoporosis: a randomized controlled trial. J Gen Intern Med 2007, 22:362-367.
• [24]Glynn RJ, Brookhart MA, Stedman M, Avorn J, Solomon DH: Design of cluster-randomized trials of quality improvement interventions aimed at medical care providers. Med Care 2007, Suppl 2:38-43.
• [25]Puffer S, Torgerson D, Watson J: Evidence for risk of bias in cluster randomised trials: review of recent trials published in three general medical journals. BMJ 2003, 327:785-789.
• [26]Shah S, Peat JK, Mazurski EJ, Wang H, Sindhusake D, Bruce C, Henry RL, Gibson PG: Effect of peer led programme for asthma education in adolescents: cluster randomised controlled trial. BMJ 2001, 322:583-585.
• [27]Chapman S, Cornwall J, Righetti J, Sung L: Preventing dog bites in children: randomised controlled trial of an educational intervention. BMJ 2000, 320:1512-1513.
• [28]Carman WF, Elder AG, Wallace LA, McAulay K, Walker A, Murray GD, Stott DJ: Effects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: a randomised controlled trial. Lancet 2000, 355:93-97.
• [29]Campbell MJ, Donner A, Klar N: Developments in cluster randomized trials and Statistics in Medicine. Stat Med 2007, 26:2-19.
• [30]Donner A, Klar N: Pitfalls of and controversies in cluster randomization trials. Am J Public Health 2004, 94:416-422.
• [31]Martin DC, Diehr P, Perrin EB, Koepsell TD: The effect of matching on the power of randomized community intervention studies. Stat Med 1993, 12:329-338.
• [32]Grosskurth H, Mosha F, Todd J, Mwijarubi E, Klokke A, Senkoro K, Mayaud P, Changalucha J, Nicoll A, ka-Gina G: Impact of improved treatment of sexually transmitted diseases on HIV infection in rural Tanzania: randomised controlled trial. Lancet 1995, 346:530-536.
• [33]Lang E, Afilalo M, Vandal AC, Boivin JF, Xue X, Colacone A, Leger R, Shrier I, Rosenthal S: Impact of an electronic link between the emergency department and family physicians: a randomized controlled trial. CMAJ 2006, 174:313-318.
• [34]Griffiths C, Foster G, Barnes N, Eldridge S, Tate H, Begum S, Wiggins M, Dawson C, Livingstone AE, Chambers M, Coats T, Harris R, Feder GS: Specialist nurse intervention to reduce unscheduled asthma care in a deprived multiethnic area: the east London randomised controlled trial for high risk asthma (ELECTRA). BMJ 2004, 328:144.
• [35]Althabe F, Buekens P, Bergel E, Belizan JM, Campbell MK, Moss N, Hartwell T, Wright LL: Guidelines Trial Group: A behavioral intervention to improve obstetrical care. N Engl J Med 2008, 358:1929-1940.
• [36]Campbell MJ: Cluster randomized trials in general (family) practice research. Stat Methods Med Res 2000, 9:81-94.
• [37]Klar N, Donner A: The merits of matching in community intervention trials: a cautionary tale. Stat Med 1997, 16:1753-1764.
• [38]Raudenbush SW, Martinez A, Spybrook J: Strategies for Improving Precision in Group-Randomized Experiments. Educational Evaluation and Policy Analysis 2007, 29:5-29.
• [39]Donner A, Taljaard M, Klar N: The merits of breaking the matches: a cautionary tale. Statist Med 2007, 26:2036-2051.
• [40]Foy R, Penney GC, Grimshaw JM, Ramsay CR, Walker AE, MacLennan G, Stearns SC, McKenzie L, Glasier A: A randomised controlled trial of a tailored multifaceted strategy to promote implementation of a clinical guideline on induced abortion care. BJOG 2004, 111:726-733.
• [41]Pocock SJ, Simon R: Sequential treatment assignment with balancing for prognostic factors in the controlled clinical trial. Biometrics 1975, 31:103-115.
• [42]Kernan WN, Viscoli CM, Makuch RW, Brass LM, Horwitz RI: Stratified randomization for clinical trials. J Clin Epidemiol 1999, 52:19-26.
• [43]Therneau TM: How many stratification factors are “too many” to use in a randomization plan? Control. Clin Trials 1993, 14:98-108.
• [44]Feder G, Davies RA, Baird K, Dunne D, Eldridge S, Griffiths C, Gregory A, Howell A, Johnson M, Ramsay J, Rutterford C, Sharp D: Identification and Referral to Improve Safety (IRIS) of women experiencing domestic violence with a primary care training and support programme: a cluster randomised controlled trial. Lancet 2011, 378:1788-1795.
• [45]Taves DR: Minimization: a new method of assigning patients to treatment and control groups. Clin Pharmacol Ther 1974, 15:443-453.
• [46]Scott NW, McPherson GC, Ramsay CR, Campbell MK: The method of minimization for allocation to clinical trials: a review. Control Clin Trials 2002, 23:662-674.
• [47]Wade A, Pan H, Eaton S, Pierro A, Ong E: An investigation of minimisation criteria. BMC Med Res Methodol 2006, 6:11. BioMed Central Full Text
• [48]Taves DR: The use of minimization in clinical trials. Contemp Clin Trials 2010, 31:180-184.
• [49]Treasure T, MacRae KD: Minimisation: the platinum standard for trials? Randomisation doesn’t guarantee similarity of groups; minimisation does. BMJ 1998, 317:362-363.
• [50]Committee for Proprietary Medicinal Products (CPMP): Committee for Proprietary Medicinal Products (CPMP): points to consider on adjustment for baseline covariates. Stat Med 2004, 23:701-709.
• [51]Berger VW: Minimization, by its nature, precludes allocation concealment, and invites selection bias. Contemp Clin Trials 2010, 31:406.
• [52]Taves DR: Minimization does not by its nature preclude allocation concealment and invite selection bias, as Berger claims. Contemp Clin Trials 2011, 32:323.
• [53]Efron B: Forcing a sequential experiment to be balanced. Biometrika 1971, 58:403-417.
• [54]Stigsby B, Taves DR: Rank-Minimization for balanced assignment of subjects in clinical trials. Contemp Clin Trials 2010, 31:147-150.
• [55]Hofmeijer J, Anema PC, van der Tweel I: New algorithm for treatment allocation reduced selection bias and loss of power in small trials. J Clin Epidemiol 2008, 61:119-124.
• [56]Han B, Enas NH, McEntegart D: Randomization by minimization for unbalanced treatment allocation. Stat Med 2009, 28:3329-3346.
• [57]Begg CB, Iglewicz B: A treatment allocation procedure for sequential clinical trials. Biometrics 1980, 36:81-90.
• [58]Atkinson AC: Optimum biased-coin designs for sequential treatment allocation with covariate information. Stat Med 1999, 18:1741-1752. discussion 1753–1755
• [59]Senn S, Anisimov VV, Fedorov VV: Comparisons of minimization and Atkinson's algorithm. Stat Med 2010, 29:721-730.
• [60]Aickin M: Randomization, balance, and the validity and efficiency of design-adaptive allocation methods. Journal of Statistical Planning and Inference 2001, 94:97-119.
• [61]Rosenberger WF, Sverdlov O: Handling Covariates in the Design of Clinical Trials. Stat Sci 2008, 23:404-419.
• [62]Ivers NM, Tu K, Francis J, Barnsley J, Shah B, Upshur R, Kiss A, Grimshaw JM, Zwarenstein M: Feedback GAP: study protocol for a cluster-randomized trial of goal setting and action plans to increase the effectiveness of audit and feedback interventions in primary care. Implement Sci 2010, 5:98. BioMed Central Full Text
• [63]Minim: allocation by minimisation in clinical trials by Stephen Evans, Patrick Royston and Simon Dayhttp://www-users.york.ac.uk/~mb55/guide/minim.htm webcite
• [64]Moulton LH: Covariate-based constrained randomization of group-randomized trials. Clin Trials 2004, 1:297-305.
• [65]Perry M, Faes M, Reelick MF, Olde Rikkert MG, Borm GF: Studywise minimization: A treatment allocation method that improves balance among treatment groups and makes allocation unpredictable. J Clin Epidemiol 2010, 63:1118-1122.
• [66]Xiao L, Lavori PW, Wilson SR, Ma J: Comparison of dynamic block randomization and minimization in randomized trials: a simulation study. Clin Trials 2011, 8:59-69.
• [67]Carter BR, Hood K: Balance algorithm for cluster randomized trials. BMC Med Res Methodol 2008, 8:65. BioMed Central Full Text
• [68]Chaudhary MA, Moulton LH: A SAS macro for constrained randomization of group-randomized designs. Comput Methods Programs Biomed 2006, 83:205-210.
• [69]Sismanidis C, Moulton LH, Ayles H, Fielding K, Schaap A, Beyers N, Bond G, Godfrey-Faussett P, Hayes R: Restricted randomization of ZAMSTAR: a 2 x 2 factorial cluster randomized trial. Clin Trials 2008, 5:316-327.
• [70]Berger VW: A review of methods for ensuring the comparability of comparison groups in randomized clinical trials. Rev Recent Clin Trials 2006, 1:81-86.
• [71]Comparative Obstetric Mobile Epidural Trial (COMET) Study Group UK: Effect of low-dose mobile versus traditional epidural techniques on mode of delivery: a randomised controlled trial. Lancet 2001, 358:19-23.