Run-in Periods in Randomized Trials: Implications for the Application of Results in Clinical Practice

• Published in: JAMA : the journal of the American Medical Association Vol. 279; no. 3; pp. 222 - 225
• Main Authors: Pablos-Méndez, Ariel, Barr, R. Graham, Shea, Steven
• Format: Journal Article
• Language: English
• Published: Chicago, IL American Medical Association 21.01.1998
• Subjects: Biological and medical sciences; Clinical Protocols; Clinical trials; Data Interpretation, Statistical; Drug testing; Medical sciences; Patient Selection; Public health. Hygiene; Public health. Hygiene-occupational medicine; Randomized Controlled Trials as Topic; Research Design; Statistics as Topic; Teaching. Deontology. Ethics. Legislation; Human; Test validation; Randomization; Placebo; Running; Clinical trial; Decision criterion; Public health; Medical application
• ISSN: 0098-7484; 1538-3598
• DOI: 10.1001/jama.279.3.222

Prerandomization run-in periods are being used to select or exclude patients in an increasing number of clinical trials, but the implications of run-in periods for interpreting the results of clinical trials and applying these results in clinical practice have not been systematically examined. We analyzed illustrative examples of reports of clinical trials in which run-in periods were used to exclude noncompliant subjects, placebo responders, or subjects who could not tolerate or did not respond to active drug. The Physicians' Health Study exemplifies the use of a prerandomization run-in period to exclude subjects who are nonadherent, while recent trials of tacrine for Alzheimer disease and carvedilol for congestive heart failure typify the use of run-in periods to exclude patients who do not tolerate or do not respond to the study drug. The reported results of these studies are valid. However, because the reported results apply to subgroups of patients who cannot be defined readily based on demographic or clinical characteristics, the applicability of the results in clinical practice is diluted. Compared with results that would have been observed without the run-in period, the reported results overestimate the benefits and underestimate the risks of treatment, underestimate the number needed to treat, and yield a smaller P value. The Cardiac Arrhythmia Suppression Trial exemplifies the use of an active-drug run-in period that enhances clinical applicability by selecting a group of study subjects who closely resembled patients undergoing active clinical management for this problem. Run-in periods can dilute or enhance the clinical applicability of the results of a clinical trial, depending on the patient group to whom the results will be applied. Reports of clinical trials using run-in periods should indicate how this aspect of their design affects the application of the results to clinical practice.