Correlation-adjusted estimation of sensitivity and specificity of two diagnostic tests

Summary. Models for multiple-test screening data generally require the assumption that the tests are independent conditional on disease state. This assumption may be unreasonable, especially when the biological basis of the tests is the same. We propose a model that allows for correlation between two diagnostic test results. Since models that incorporate test correlation involve more parameters than can be estimated with the available data, posterior inferences will depend more heavily on prior distributions, even with large sample sizes. If we have reasonably accurate information about one of the two screening tests (perhaps the standard currently used test) or the prevalences of the populations tested, accurate inferences about all the parameters, including the test correlation, are possible. We present a model for evaluating dependent diagnostic tests and analyse real and simulated data sets. Our analysis shows that, when the tests are correlated, a model that assumes conditional independence can perform very poorly. We recommend that, if the tests are only moderately accurate and measure the same biological responses, researchers use the dependence model for their analyses.     

SOCIAL SECURITY AND AGGREGATE CAPITAL ACCUMULATION REVISITED: DYNAMIC SIMULTANEOUS ESTIMATES IN A WEALTH-GENERATION MODEL

This paper re-examines Feldstein's(1974, 1982)results of the effect of social security on private capital accumulation in the context of a simultaneous-equation model of capital accumulation. The model incorporates dynamic feedback effects in capital accumulation and is estimated by FIML to incorporate theoretical restrictions that are tested against the data. It is then simulated as a full dynamic model to analyze the long-run effect of SSW on private capital accumulation. The simulated effects are in the same direction as found by Feldstein, but are considerably weaker.     

Life change,health status and life satisfaction: A reconsideration

Recent research has suggested that life changes may be unrelated to health status indices and to overall satisfaction with life. Yet research has also reported that life changes appear to be related to measures of psychological distress. To attend further to clarification of the role of life change as a predictor of health status and life satisfaction, this paper examines the relationship between negative life change self-reports and indices of health status and life satisfaction. The data come from a survey of 1423 Northwestern Wisconsinites interviewed in 1974 by the Wisconsin Survey Research Laboratory. The findings indicate that self-reports of negative life changes were related to overall life satisfaction, controlling for health status, feelings of alienation/attachment, and personal disruption. Implications of the findings are discussed in conclusion.     

Estimatingdendroctonus frontalis (Coleoptera: Scolytidae) daily infestation dynamics

Mathematical procedures are given to estimate infestation totals and daily life stage arrivals, departures, and mortality ofDendroctonus frontalis Zimmermann for an infested tree in the field. These estimates are based on minimal sample data and are designed to utilize all available information. Daily arrival estimates for larvae, pupae, and callow adults are obtained by indirect analysis without direct observation of these stages. The procedures are applied to 147 infested trees, and the results are transformed to a common time basis to obtain daily expectations by life stage for an “average” tree. These expectations suggest optimal times for field sampling or relative times of sampling when optimal times are missed. Expected daily arrival distributions by life stage for a single egg and a single attacking adult are given. Procedures are given for utilizing collateral information to obtain an infestation total and daily arrival estimates for a boundary life stage. The results of this study are applicable to anyD. frontalis field study, and the procedures given are applicable to any bark inhabiting insect having similar habits.     

Meeting the Needs of the Adoption Triangle Through Open Adoption: The Birthmother

Open adoption is a relatively new and controversial practice. However, in many cultures this practice is traditional. In this first of a series of articles, the affect of open adoption upon birthparents is discussed. The open process facilitates appropriate grieving, enables decision making and furthers the growth of the birthmother.     

Home care reimbursement for technology-dependent children: Its impact on parental distress

The distress of 52 parents with a technology-dependent child at home is measured using a standardized psychological inventory. Fifty-eight percent of these parents report enough symptoms to classify them as needing psychiatric intervention. Cost savings to third-party payers are accelerating the trend toward home care (rather than institutionalized care). Yet, these findings point to an underestimated cost to families in terms of parents' psychological well-being. One factor associated with less distress for mothers is having services reimbursed through the Medicaid Model Waiver Program, which provides a comprehensive plan for home care services. In contrast, services reimbursed by private third-party payers are more variable, placing greater financial strain and uncertainty on parents, which is associated with greater psychological distress. These results suggest the need for further study of the long-term impact on parents caring for technology-dependent children at home.Reprint requests to Barbara J. Leonard, R.N., Ph.D., Maternal and Child Health Major, Division of Human Development and Nutrition, School of Public Health, Box 197 UMHC, University of Minnesota, Minneapolis, MN 55455, (612) 625-3660.This study was supported in part by BRSG Number 2-S07-RR05448-25 awarded to the University of Minnesota, School of Public Health by the Biomedical Research Grant Program, Division of Research and Resources, National Institute of Health. Additional support was provided by the Department of Health and Human Services, State of Minnesota, Academic Computing Services and Systems, University of Minnesota and special project funds from the University of Minnesota School of Public Health.Barbara J. Leonard is an Assistant Professor and Chair of the Maternal and Child Health Major, Division of Human Development and Nutrition, School of Public Health, University of Minnesota, MN 55455. Her research interests include children with developmental disabilities, their parents, and siblings. She received her Ph.D. from the University of Minnesota.Janny Dwyer Brust is a Research Fellow in the Maternal and Child Health Major at the University of Minnesota. Her research interests include issues related to the care of chronically ill children and sexually abused children. She received her M.P.H. from the University of Minnesota.Joan Patterson is an Assistant Professor in the Maternal and Child Health Major and Associate Director of the Center for Children with Chronic Illness and Disability at the University of Minnesota. Her research interests include family adaptation to chronic illness and family stress and coping. She received her Ph.D. from the University of Minnesota.