Finite mixture models with concomitant information: assessing diagnostic criteria for diabetes

The World Health Organization (WHO) diagnostic criteria for diabetes mellitus were determined in part by evidence that in some populations the plasma glucose level 2 h after an oral glucose load is a mixture of two distinct distributions. We present a finite mixture model that allows the two component densities to be generalized linear models and the mixture probability to be a logistic regression model. The model allows us to estimate the prevalence of diabetes and sensitivity and specificity of the diagnostic criteria as a function of covariates and to estimate them in the absence of an external standard. Sensitivity is the probability that a test indicates disease conditionally on disease being present. Specificity is the probability that a test indicates no disease conditionally on no disease being present. We obtained maximum likelihood estimates via the EM algorithm and derived the standard errors from the information matrix and by the bootstrap. In the application to data from the diabetes in Egypt project a two-component mixture model fits well and the two components are interpreted as normal and diabetes. The means and variances are similar to results found in other populations. The minimum misclassification cutpoints decrease with age, are lower in urban areas and are higher in rural areas than the 200 mg dl^-1 cutpoint recommended by the WHO. These differences are modest and our results generally support the WHO criterion. Our methods allow the direct inclusion of concomitant data whereas past analyses were based on partitioning the data.     

GENDER, EARNINGS, AND THE ENGLISH SKILL ACQUISITION OF HISPANIC WORKERS IN THE UNITED STATES

Using the 1980 and 1990 Public Use Microdata Samples, we find that labor market outcomes associated with English proficiency vary with respect to gender. For example, a synthetic cohort analysis provides evidence of gender-related differences in Hispanic workers' English skill acquisition. Moreover, we observe that Hispanic women face a lower English deficiency earnings penalty that rises more sharply with education than the penalty obtained by their otherwise similar male peers. Finally, English fluency appears to serve as a stronger occupational sorting mechanism for women than men. ( JEL J3, J1)     

Practicing managed care in the academic medical center

The purpose of this article is to outline the contrasts between the traditional AMC and an organization oriented toward the delivery of population-based managed care. Academic medical centers differ from one another considerably in the extent to which they serve as quaternary care community resources, the degree to which they emphasize primary care in training and care delivery, and the amount of research undertaken. Nor is there a single organizational structure for managed care; successful managed care is practices in IPAs, multispecialty groups, PHOs, and staff-model HMOs. Nonetheless, the contrasts outlined here between AMCs and managed care organizations (MCOs) are valid in most cases.     

The implementation of the healthy cities project in developing countries: lessons from Chittagong

The Chittagong Healthy City Project was carried out in late 1994 in Chittagong, Bangladesh. This paper presents findings of an evaluation of the project based upon internationally generated process indicators related to the institutional aspects of the project. The following issues are discussed with regard to project implementation: the institutional organization of local authorities, institutions' conceptual understanding of the project, formal insertion of the project into public authorities' activities, institutional leadership of the project, central-local relations, the lack of interministerial coordination, the project's office, international projects, and community organization. Giving consideration to these issues may help program planners detect problems in forthcoming projects prior to their implementation.     

Characterizations,length-biasing,and infinite divisibility

SupposeL(X) is the law of a positive random variableX, andZ is positive and independent ofX. Admissible solution pairs (L(X),L(Z)) are sought for the in-law equation $\hat X \cong X o Z$ °Z, where $L\left( {\hat X} \right)$ is a weighted law constructed fromL(X), and ° is a binary operation which in some sense is increasing. The class of weights includes length biasing of arbitrary order. When ° is addition and the weighting is ordinary length biasing, the class of admissibleL(X) comprises the positive infinitely divisible laws. Examples are given subsuming all known specific cases. Some extensions for general order of length-biasing are discussed.     

Changes in physician and non-physician relationships

At the end of World War II, one-third of the nation's hospital administrators were physicians. During the 1950's through the mid-1980's a new breed of masters'level administrator, with well-honed coordinating skills, orchestrated a major expansion of new programs, services, and facilities. With the advent of the Medicare prospective payment system (PPS), more governing boards restructured their administrative staffs with corporate titles. Meanwhile, physicians sensed that trustees were becoming far more concerned with bottom line performance to repay a mounting debt that hospitals had incurred to remain technologically competitive. Since mergers and integrated health systems by themselves will be unable to generate significant operating efficiencies, governing boards will be forced to change direction and shift back to recruiting physicians as their CEOs or in other senior positions to assure themselves of the clinical leadership required to implement the managed care concepts of reducing utilization and cost, and simultaneously enhancing quality of patient care.     

Validating quality indicators. Quality as relationship between structure, process, and outcome

Theory and research have not kept pace with the growing interest in evaluating quality of mental health care, resulting in the use of unvalidated quality indicators. A framework for validating quality indicators is offered by which quality is viewed as the relationship between service structures, processes, and outcomes. Adoption of this framework will facilitate the measurement of quality using valid indicators and should be useful to agencies in their continuous quality improvement efforts. Valid information about the quality of mental health care services will help purchasers and consumers make more informed health care decisions.     

Implementation and process evaluation of a student "school-as-community" group. A component of a school-based drug abuse prevention program

Little documentation exists regarding the functioning of formalized adolescent groups as drug abuse prevention agents. Two studies are described that were conducted at high schools whose students are at high risk for drug abuse. Twenty-one schools were randomly assigned to one of three conditions: (a) standard care, (b) classroom drug abuse education only, or (c) classroom plus school-as-community. Results of the first study indicated that the school-as-community component--which involved weekly meetings and periodic events at seven schools--was implemented as planned, drug abused focused, and perceived as productive in discouraging drug abuse. In the second study, staff in the classroom plus school-as-community condition self-reported involvement in the greatest number of community activities across the school year, compared with staff from the other two conditions. These two studies support the feasibility of formalized groups of high-risk youth to promote drug-free events.