Enrollment factors and preexisting medical conditions in a prepaid capitated plan: a comparison of university and nonuniversity clinic enrollees

Journal of Family Practice, Nov, 1989 by Kathleen E. Ellsbury, Eric B. Larson, Wendy Raskind, Daniel E. Montano, David Kuykendall

Prepaid health care plans are serving an increasing portion of the health care needs in the United States. The benefits and disadvantages of affiliations between prepaid health care plans and academic centers have been described elsewhere.(1-5) One of the most rapidly growing types of plan is the capitated medical plan, which pays physicians a specific amount per member per month for each enrollee assigned to them.(6-7) Capitated medical plans have attracted considerable attention from primary care specialties because of their potential to provide patient care revenues, educational benefits, and research opportunities.(8-10)

There are, however, several potential problems for academic centers affiliating with capitated plans. Previous studies have suggested a more costly case-mix of enrollees in teaching hospitals when compared with enrollees in nonteaching hospitals,(5,11,12) though the evidence varies." For example, Kosecoff et al(l4) found significant chronic morbidity among patients in 15 general internal medicine clinics in teaching hospitals, though Lion and Altman" found only a 10% to 15% increase in complexity among patients in hospital outpatient departments compared with patients in private practice settings, based on physician assessment of patient illness.

There are many reasons insured patients with significant health problems might seek care at an academic medical center, among which are the center's state-of-the-art technology and the availability of subspecialists and special research programs.(16-17) The importance of a preexisting physician-patient relationship in prepaid plan enrollment decisions has been emphasized in previous studies. 18-10 This relationship is less likely in university clinics, where because of the nature of medical training, physician turnover is higher than in private practice settings. No study has examined the factors influencing capitated plan members to enroll in university clinics as compared with those factors influencing members to enroll in nonuniversity clinics.

It was hypothesized that a university practice might enroll a different population than nonuniversity practices because the patients were sicker and needed more resources. This enrollment selection would adversely affect the economic viability of medical practices in academic centers that care for a large patient population belonging to prepaid plans. To explore this hypothesis, university and nonuniversity enrollees were compared at the time of enrollment into a prepaid plan, focusing on the following factors: demographic characteristics, self-reported health status and preexisting medical conditions, and previous health care utilization during the year prior to the survey. The same enrollees were also compared with regard to factors influencing selection of health care plan, clinic, and physician. METHODS Description of Prepaid Plan

The survey was distributed to a random sample of new enrollees of a 5-year-old prepaid capitated network-model health maintenance organization (HMO) in western Washington State in 1986. The plan was affiliated with clinics employing five or more physicians and was open to enrollment only through employers.

Under the plan's guidelines each enrollee was required to choose a group practice affiliated with the plan and to choose a primary care physician (family physician, internist, pediatrician, or obstetrician-gynecologist) at or before the time of first utilization of care under the plan. The term clinic in this paper refers to the individual practice groups studied. University clinic enrollees were enrollees who were assigned to a primary care physician at the university outpatient facilities and, with few exceptions, obtained all medical care at university facilities. Six nonuniversity clinics affiliated with the capitated plan were chosen as candidates for the study because they represented a spectrum of practice types ranging from primary-care-based clinics to multispecialty groups in urban, suburban, and rural settings. Five of the six nonuniversity clinics agreed to participate. The number of enrollees at each participating clinic ranged from 1953 to 5080. The clinic that chose not to participate was a suburban family practice clinic that had affiliated with the plan relatively recently. Three of the participating clinics (including the university) were large multispecialty urban clinics, one was a small suburban multispecialty clinic, and two were suburban and rural practices where family practitioners were the predominant primary care providers.

All clinics were located within 60 miles of Seattle, Washington. There were 2871 enrollees at the University of Washington clinics and 15,203 enrollees at the five nonuniversity clinics studied (average 3005 enrollees per clinic). Population Studied

The central administration of the prepaid plan provided a randomly generated list of new enrollees who had joined the plan after January 1, 1986, from which a subset of enrollees was randomly selected. Because the primary goal of the study was to compare new enrollees in university clinics with new enrollees in nonuniversity clinics, the sample included 400 enrollees in the university clinics (14% of total university enrollees) and 759 enrollees in the nonuniversity clinics (5% of the nonuniversity enrollees). A power calculation predicted that a sample size of 200 per group would have a 90% chance of detecting a 15% difference (0.6 points on a 4-point scale) between groups (P < .05).(21)