Weighing gains and losses in criterion validity studies with test-based enrollment

Criterion validity studies sometimes use designs with test-based enrollment schemes. In such incomplete studies, a Reference Instrument (RI) is applied to unequal sampling fractions of subjects previously identified as positives or negatives by a new Test Instrument (TI+ and TI-). Focusing on sensitivity (Se) and specificity (Sp), this article addresses some issues concerning the precision of estimates, study costs, as well as the acceptability/convenience to subjects. For that purpose, examples are provided whereby three indicators-statistical efficiency differential (deltaS), cost differential (deltaC), and (in)convenience differential (deltaI)-are contrasted and discussed. Although a clear, fast-and-ready answer as to what constitutes an optimal study cannot be given, the article offers a rationale for weighing gains and losses. Among several scenarios, it is shown that an appropriately chosen incomplete study design may be as statistically efficient as one with a complete sampling scheme, yet is able to offer a ca. 15% cost reduction and about 20% fewer individuals needing to endure an invasive or logistically cumbersome RI. A special emphasis on the planning stages of an investigation is called for, precisely when the level of statistical precision the researcher is willing to accept can be weighed against the available budget and the degree of stress put on the subject that ought to be avoided.     

Biased enrollment of Medicare beneficiaries in HMO plans--implications for Medicare costs

Policymakers assumed that the enrollment of Medicare beneficiaries in health maintenance organization (HMO) plans would generate significant cost savings for Medicare. The Health Care Financing Administration (HCFA) calculates the reimbursement to HMOs per Medicare beneficiary on the basis of individual and community-specific characteristics. Estimates of the individual-specific profitability rate for enrolling an individual in a Medicare HMO risk plan suggest that the probability of enrollment in HMOs increases with a higher profitability score. The probability of not enrolling high-loss cases is found to be high, indicating that the biased selection in HMO plans actually increases the overall cost of running the Medicare program.     

Reduced emergency department utilization associated with school-based clinic enrollment.

PURPOSE: To evaluate the change in emergency department utilization before and after enrollment in a school-based clinic (SBC). METHODS: This study was a retrospective cohort study comparing emergency department visit rate before and after SBC enrollment based on chart review. An initial cohort of 10- to 15-year-olds who used a local emergency department was divided into two samples: those who had been enrolled in the SBC and those who had not. Emergency department charts were reviewed for visits that occurred during the initial year and two subsequent school years. The change in visit rate for each sample group was measured for each school year evaluated. RESULTS: The initial cohort consisted of 2852 youth, 344 of whom who lived in the high school attendance zone. Of these, the number of students enrolled in both the high school and the SBC was 43; the number enrolled in the high school but not in the clinic was 48. The emergency department visit rate decreased for both groups for each school year evaluated; however, this decrease was significant only for the SBC sample with a 41% to 57% decrease in emergency department utilization, 18% greater than the decrease in students who did not use the SBC. CONCLUSIONS: Accessible, prevention-oriented health care provided in a SBC can decrease the utilization of episodic health care in an emergency department.     

Mandatory HMO enrollment in Medicaid: the issue of freedom of choice

In areas where HMOs have enrolled a small proportion of the general population, physician participation is less in mandatory HMO programs for Medicaid beneficiaries than in fee-for-service Medicaid. But where HMOs have enrolled over one-quarter of the general population, participation rates are indistinguishable under the two systems. In those areas, mandatory enrollment restricts freedom of choice of provider. A plausible reason for this is that individual practice associations, which contract with large numbers of physicians with both fee-for-service and HMO patients, are becoming the lead form of HMO.     

Health care experience among employees prior to and after enrollment in a prepaid health insurance plan (HMO)

Company medical and benefit records of employees who were enrolled in prepaid health insurance plans (HMOs) in Minneapolis, Washington, D.C., and Seattle were reviewed for hospital and surgical utilization prior to as well as after their enrollment. Comparisons were made for the same calendar periods with closely matched employees who were covered by Blue Cross/Blue Shield (BC/BS). The results indicate that after enrollment the HMO subjects at each location had lower rates for hospital and surgical utilization than the BC/BS controls. For the period prior to enrollment, during which time coverage was through BC/BS, the prospective HMO subjects at two locations had lower hospital and surgical utilization than the controls. Possible explanations of this potential self-selection bias are discussed.     

安徽省立儿童医院门诊楼方案设计回顾

本文对安徽省立儿童医院门诊楼方案设计作简要的介绍，并就总体布局、交通流线、功能组织等方面作了较为深入的分析。医疗建筑设计应以人为本，使医疗空间融入环境，让患者感受到和谐自然，并指出关注人的整体健康是现代医院设计的必然趋势。