Use of HMOs-Reply

In Reply.—  We share Wersinger and Shelton's interest in research concerning HMO enrollees' utilization after initial enrollment and suggest that readers consult recently published studies.^1-3 Subsequent hospital utilization increased in two of the three Rochester HMOs cited by Wersinger and in two of the three HMOs serving AT&T employees described by Dunn and Mitchell.¹ Roghmann and colleagues⁴ concluded "that during initial marketing when the penetration rate is low, selective enrollment can have an impact on plan viability of equal importance as effective management to reduce hospitalization." To what extent do lower hospital use rates for HMOs reflect effective management and controls instead of or in addition to enrollment characteristics? The answer is unknown and seems to differ depending on the HMO in question.We also agree that disenrollment from alternative and traditional health provision systems is an important question. Disenrollment makes longitudinal studies difficult when consumers have