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American Journal of Epidemiology Vol. 154, No. 9 : 873-880
Copyright © 2001 by The Johns Hopkins University School of Hygiene and Public Health

PRACTICE OF EPIDEMIOLOGY

Effect of Early Patient Enrollment on the Time to Completion and Publication of Randomized Controlled Trials

Anna-Bettina Haidich1 and John P. A. Ioannidis1,2

1 Clinical Trials and Evidence-based Medicine Unit, Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece.
2 Department of Medicine, Tufts University School of Medicine, Boston, MA.

The authors evaluated whether early enrollment affects the significance of the results and the time to completion and publication of randomized controlled trials. Seventy-seven efficacy randomized controlled trials (total enrollment, 28,992 patients) initiated by the Acquired Immunodeficiency Syndrome Clinical Trials Group between 1986 and 1996 were evaluated. After adjustment for target sample size, for each 10-fold increase in the first-month accrual, the odds of a trial reaching statistically significant results increased 2.8-fold (p = 0.040). The relative enrollment during the first month over target sample size (hazard ratio (HR) = 1.40 per 10 percent increase, p = 0.004) and masking (HR = 1.78 for double-blind vs. single or unblinded studies, p = 0.031) were the major predictors of faster completion. Rapid early accrual (HR = 1.09 per 10 additional patients accrued the first month, p = 0.011) and statistical significance in favor of an experimental arm (HR = 2.47, p = 0.004) independently predicted faster publication. Early enrollment is a strong predictor of whether a study will reach formal statistical significance, and it can offer predictive information on the time needed to complete the study and publish its findings. Ongoing unpublished studies and their enrollment rates may need to be considered when interpreting the accumulated evidence.

bias (epidemiology); double-blind method; patient participation; patients; randomized controlled trials; sample size; statistics

Abbreviations: ACTG, Acquired Immunodeficiency Syndrome Clinical Trials Group; AIDS, acquired immunodeficiency syndrome; AUC, area under the curve; CI, confidence interval; HIV, human immunodeficiency virus; HR, hazard ratio; RCT, randomized controlled trial; ROC, receiver operating characteristic


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