Relationship between rate of patient enrollment and quality of clinical center performance in two multicenter trials in ophthalmology

Those responsible for managing and overseeing multicenter clinical trials often express concern that differential rates of patient enrollment among participating clinical centers may be reflected in poorer compliance with study protocols or poorer patient care in the centers enrolling fewer patients. The purposes of the present investigation were (1) to determine whether rate of patient enrollment was related to other measures of clinical center performance in two multicenter clinical trials in ophthalmology, the Macular Photocoagulation Study (MPS) and the Early Treatment Diabetic Retinopathy Study (ETDRS), and (2) to compare findings from these two studies with findings reported from cooperative oncology groups. Percent of major data forms ever failing computerized edit was the only measure of performance examined that demonstrated a strong positive relationship to rate of patient enrollment in both studies under both analytic approaches employed (F test for linear trend in means and Spearman's rank correlation). In the MPS, but not in the ETDRS, percent of patients who had missed all visits scheduled during the past 12 months (inactive patients) also was related to rate of patient enrollment. However, the major finding from this investigation has been that it is not possible to predict overall performance of an individual clinical center based on rate of patient enrollment. Clinical centers enrolling fewer patients in these multicenter clinical trials performed in some areas as well as or better than centers enrolling larger numbers of patients.