Introduction: Planning cluster randomized studies requires special attention due to their specific design. To achieve balance on a cluster level as well as on individual level, it is necessary to apply randomization techniques which involve restricted randomization. Objective: Determine randomization techniques as well as their frequency in protocols for cluster randomized trials. Materials and method: Searching the MEDLINE bibliographic database, there were 1020 bibliographic units, the analysis included only the protocols for cluster randomized trials, which was a total of 169 trials. Data on randomization techniques, units of randomization and publication years of protocols were extracted. Results: The randomization technique with most frequency was stratification (35.9%). After stratification the most frequent was simple randomization (13.5%), followed by a combination of block and stratification (10%), block randomization (9.4%) and matching (9.4%). The most frequent units of randomization were health facilities (52%). The number of published protocols statistically increases during time (p<0.01). Conclusion: The most frequent randomization technique used by researchers is restricted randomization
Toerien M, Brookes S, Metcalfe C, Salis I, De, Tomlin Z, et al. A review of reporting of participant recruitment and retention in RCTs in six major journals. 2009;1–12.
2.
Mayer D, M. Essential Evidence-Based Medicine. 2010;
3.
Manju A, Candel M, Berger M. Sample size calculation in cost-effectiveness cluster randomized trials : optimal and maximin approaches. 2014;
4.
Wang D. Clinical Trials.
5.
Lenzen M, Domburg R, Van, Hoeks S, Mc E. Tools & Techniques Methodology and Statistics : Randomisation in clinical trials. 2013;410–1.
6.
Herbert R. Randomisation in clinical trials. 2005;
7.
Mcpherson G, Campbell M, Elbourne D. Use of randomisation in clinical trials : a survey of UK practice. Trials.
8.
Trials. Available from: Trials. 2012;(1).
9.
Ivers N, Halperin I, Barnsley J, Grimshaw J, Shah B, Tu K. Allocation techniques for balance at baseline in cluster randomized trials : a methodological review. Trials. 2012;(1).
10.
Lewsey J. Comparing completely and stratiÿed randomized designs in cluster randomized trials when the stratifying factor is cluster size : a simulation study. 2004;897–905.
11.
Esserman D, Allore H, Travison T. The Method of Randomization for Cluster-Randomized Trials : Challenges of Including Patients with Multiple Chronic Conditions. 2016;2–7.
12.
Hayes R, Lhm. Cluster Randomised Trials. 2009;
13.
Froud R, Eldridge S, Do K, Vcc M, Quality D. Quality of cluster randomized controlled trials in oral health : a systematic review of reports published between. 2005;3–14.
14.
Isaakidis P, Ioannidis J. Evaluation of Cluster Randomized Controlled Trials in Sub-Saharan Africa. 2003;(9):921–6.
15.
Components D, Stat V, World B. Design and Analysis of Group-Randomized Trials : A Review of Recent Practices. 2004;(3):393–9.
16.
Simpson J, Klar N, Donner A. Accounting for Cluster Randomization : A Review of Primary Prevention Trials. 1990;(10).
17.
Eldridge S, Ashby D, Feder G, Rudnicka A, Ukoumunne O. Lessons for cluster randomized trials in the twenty-first century: a systematic review of trials in primary care. 2004;
18.
Murray D, Pals S, Blitstein J, Alfano C, Lehman J. Design and Analysis of Group-Randomized Trials in Cancer : A Review of Current Practices. 2008;483–91.
19.
Originalni Radovi.
20.
Ivers N, Taljaard M, Dixon S, Bennett C, Mcrae A, Taleban J. Impact of CONSORT extension for cluster randomised trials on quality of reporting and study methodology : review of random sample of 300 trials. 2000;1–14.
21.
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. :785–7.
22.
Wakelin M, Feder G. Internal and external validity of cluster randomised trials : systematic review of recent trials.
23.
Bland J. Cluster randomised trials in the medical literature : two bibliometric surveys. 2004;2–7.
24.
Campbell M, Mollison J, Steen N, Grimshaw J, Eccles M. Analysis of cluster randomized trials in primary care : a practical approach. 2000;(2):192–6.
25.
Brierley G, Ma S, Torgerson D, Watson J. Bias in recruitment to cluster randomized trials : a review of. 2012;878–86.
The statements, opinions and data contained in the journal are solely those of the individual authors and contributors and not of the publisher and the editor(s). We stay neutral with regard to jurisdictional claims in published maps and institutional affiliations.
