Reported use of data monitoring committees in the main published reports of randomized controlled trials: a cross-sectional study.

BACKGROUND: We describe a review of published main reports of randomized controlled trials (RCTs), in order to measure the frequency of reported use of data monitoring committees (DMCs) and factors associated with reported DMC use.
METHODS: Twenty-four higher impact general and specialist medical journals were handsearched for main reports of RCTs in order to provide a cross-sectional sample of trials published in the year 2000. Additionally, the same general medical journals were handsearched for 1990 to allow a comparison across time.
RESULTS: Of 662 RCTs published in 2000, 120 (18%) explicitly reported using a DMC, while 107 (16%) reported planned interim analyses. Overall, about a quarter (24%) reported at least one of these. A higher proportion of trials reported using a DMC in 2000 than 1 990 (70/282, 25% versus 21/204, 10%) in the general medical journals. Logistic regression models suggested the more important variables associated with increased reported DMC use were: later year of publication, publication in general medical journal, survival-based endpoint, multicentre trial, increasing number of patients recruited, at least one arm involving a placebo, at least one arm involving a drug, factorial design and USA involvement in the trial.
CONCLUSIONS: In 2000, about a quarter of main RCT reports mention use of a DMC. Actual use of DMCs is likely to be somewhat greater. Reporting use of a DMC was more likely for larger and longer trials among other factors. We believe the factors affecting reported use affect actual use. It is recommended that when a DMC oversees a trial, brief details should be explicitly included in the main trial paper. Standard nomenclature for DMCs is recommended.