ELSEV IER Decision Rules for Predicting Future Lipid Values in Screening for a Cholesterol Reduction Clinical Trial Lemuel A. Moy6 MD, PhD, Barry R. Davis, MD, PhD, Frank Sacks, MD, Thomas Cole, PhD, Lisa Brown, MPH, and C. Morton Hawkins, ScD zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLK From the Coordinating Center for Clinical Trials, University of Texas School of Public Health, Houston, TX (L.A.M., B.R.D., CMH.), CARE Clinical Coordinating Center, Brookline, MA (L.B.), Department of Medicine, Brigham and Women’s Hospital, Boston, MA (F.S), and Lipids Research Center, St. Louis, Ml (T.C.) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR A BSTRA CT: Recent large clinical trials have required screened patients to have serial measure- ments of an entry criteria variable, eliminating patients from further consideration if the average value is not in the eligibility range specified by the tial protocol. The increasing costs of large clinical trials required that they be executed efficiently. One way to improve efficiency would be to reduce the number of required screening measure- ments for a patient likely to be ineligible. A procedure is proposed that predicts the value of an average based on n measurements serially obtained on a patient during the screening phase when only m < n measurements are available. The employment of this procedure in a large clinical trial that uses low-density lipoprotein (LDL) cholesterol, total cholesterol, and triglycerides as entry criteria during the screening process is described. As a second example, this procedure is applied to population screening for lipid levels above a treatment threshold. The National Cholesterol Education Program recommends that the average of two LDL cholesterol measurements be used to deter- mine whether LDL cholesterol is above 130 mg/ dl, the threshold for treating patients with coronary heart disease. However, data from a sample of patients from a postin- farction population suggest that, if a single LDL cholesterol is above 146 mg/ dl, the probability is greater than 95% that the average of the two LDL cholesterol measurements will be above 130 mg/ dl. 0 Elsevier Science Inc. 1996 Controlled CZin Trials 2996; 17:536-546 KEY WORDS: Screening, lipids, multivariate normal distribution INTRODUCTION The screening process of large clinical trials represents a crucial first step on the experiment’s path to success, a step that requires the trial’s recruiters Address reprint requests to: Lenmel A. Moyt!,MD, PhD, School of Public He&h, 1200Hemran Pressler, Houston, TX 77030. Received October 13, 1994; revised June 6, 1995. Controlled Clinical Trials 17536-546 (1996) 0 Elsevier Science Inc. 1996 6.55Avenue of the Americas, New York, NY 10010 0197-2456/% /$15.00 PI1 SO197-2456(% -2