Background: A noncompleter is defined as a participant who leaves a trial before the end of the planned follow-up. Research in nursing homes is highly exposed to this problem because of high death rates.
Objectives: The aim of this trial is to assess the statistical management of noncompleters in cluster randomized trials carried out in nursing homes.
Study design and setting: A methodological review of published cluster randomized trials.
Results: We selected 37 articles. For 22 (59%) trials, the design was closed-cohort (i.e., participants included all at the same time when randomizing clusters). In those 22 closed-cohort trials, the median follow-up was 6.5 months (interquartile range 4-12). The median noncompleter rate was 19.5% and the median noncompletions due to death was 73.2%. In only one trial were the baseline characteristics of completers and noncompleters compared. Strategies to deal with noncompleters were an inflation of the planned sample size (11 trials), the use of repeated measurements of the outcome (12 trials), and the use of imputation methods when analyzing data (7 trials).
Conclusion: In cluster randomized trials of nursing homes, noncompleters are managed as for any missing data, but they are essentially due to death. Methodological and statistical developments and guidance are needed.
Keywords: Cluster randomized trials; Geriatric; Missing data; Noncompleters; Nursing homes; Statistical analysis.
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