The Sensitivity and Specificity of Markers for Event Times

The statistical literature on assessing the accuracy of risk factors or disease markers as diagnostic tests deals almost exclusively with settings where the test, Y, is measured concurrently with disease status D. In practice, however, disease status may vary over time and there is often a time lag between when the marker is measured and the occurrence of disease. One example concerns the Framingham Risk Score as a marker for the future risk of cardiovascular events, events that occur after the score is ascertained. To evaluate such a marker, one needs to take the time lag into account since the accuracy may be higher when the marker is measured closer to the time of disease occurrence. We therefore consider inference for sensitivity and specificity functions that are defined as functions of time. Semi-parametric regression models are proposed. Data from a cohort study are used to estimate model parameters. One issue that arises in practice is that event times may be censored. In this research, we extend the work by Leisenring, Pepe and Longton (1997) that dealt only with binary tests, parametric models to continuous tests, semi-parametric models and censored data. Asymptotic distribution theory for parameter estimates is produced and procedures for making statistical inference are evaluated with simulation studies. We illustrate our methods with a dataset from the Cardiovascular Health Study, relating the Framingham risk score measured at enrollment to subsequent risk of cardiovascular events

Implementation research and Asian American/Pacific Islander health

Numerous barriers prevent the translation of research into practice, especially in settings with diverse populations. Nurses are in contact with diverse populations across settings and can be an important influence to further implementation research. This paper describes conceptual approaches and methodological issues pertinent to implementation research and implications for Asian American/Pacific Islander (AAPI) health research. The authors discussed the values of using theory to guide implementation research, levels of theory that are commonly used in interventions, and decisions for theory selection. They also articulated the shortcoming of randomized controlled trials, the gold standard for testing efficacy of interventions, and present quasi-experimental designs as a plausible alternative to randomized controlled trials when research is conducted in real-world settings. They examined three types of quasi-experimental designs, the unit of analysis, the choice of dependent variables, and measurement issues that influence whether research findings and evidence-based interventions are successfully translated into practice. Practicing nurses who are familiar with the AAPI population, as well as nurse researchers who have expertise in AAPI health can play critical roles in shaping future implementation research to advance AAPI health. Nurses can provide practice-based evidence for refining evidence-supported interventions for diverse, real-world settings and theory-based interventions that are socioculturally appropriate for AAPIs. Interdisciplinary, practice-based research networks that bring multiple agencies, organizations, communities, and academic institutions together can be a mechanism for advancing implementation research for AAPI health

Femoral Artery Atherosclerosis Is Associated With Physical Function Across the Spectrum of the Ankle-Brachial Index: The San Diego Population Study.

BackgroundThe ankle-brachial index (ABI) is inadequate to detect early-stage atherosclerotic disease, when interventions to prevent functional decline may be the most effective. We determined associations of femoral artery atherosclerosis with physical functioning, across the spectrum of the ABI, and within the normal ABI range.Methods and resultsIn 2007-2011, 1103 multiethnic men and women participated in the San Diego Population Study, and completed all components of the summary performance score. Using Doppler ultrasound, superficial and common femoral intima media thickness and plaques were ascertained. Logistic regression was used to assess associations of femoral atherosclerosis with the summary performance score and its individual components. Models were adjusted for demographics, lifestyle factors, comorbidities, lipids, and kidney function. In adjusted models, among participants with a normal-range ABI (1.00-1.30), the highest tertile of superficial intima media thickness was associated with lower odds of a perfect summary performance score of 12 (odds ratio=0.56 [0.36, 0.87], P=0.009), and lower odds of a 4-m walk score of 4 (0.34 [0.16, 0.73], P=0.006) and chair rise score of 4 (0.56 [0.34, 0.94], P=0.03). Plaque presence (0.53 [0.29, 0.99], P=0.04) and greater total plaque burden (0.61 [0.43, 0.87], P=0.006) were associated with worse 4-m walk performance in the normal-range ABI group. Higher superficial intima media thickness was associated with lower summary performance score in all individuals (P=0.02).ConclusionsFindings suggest that use of femoral artery atherosclerosis measures may be effective in individuals with a normal-range ABI, especially, for example, those with diabetes mellitus or a family history of peripheral artery disease, when detection can lead to earlier intervention to prevent functional declines and improve quality of life

The influence of adult hip shape genetic variants on adolescent hip shape : Findings from a population-based DXA study

Acknowledgments: We are extremely grateful to all the families who took part in this study, the midwives for their help in recruiting them, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, and nurses. The UK Medical Research Council and the Wellcome Trust (ref: 102215/2/13/2) and the University of Bristol provide core support for ALSPAC. A comprehensive list of grants funding is available on the ALSPAC website (http://www.bristol.ac.uk/alspac/external/documents /grant-acknowledgements.pdf). GWAS data was generated at Laboratory Corporation of America (LabCorp Holdings, Burlington, NC, USA) by 23andMe and small subset was also performed at Wellcome Sanger Institute to check data quality. MF was supported by a Wellcome Trust PhD studentship (ref: 105504/Z/14/Z). LP works in the Medical Research Council Integrative Epidemiology Unit at the University of Bristol which is supported by the Medical Research Council and the University of Bristol (MC_UU_00011/1). This publication is the work of the authors and MF will serve as guarantor for the contents of this paper. None of the funders had any influence on data collection, analysis, interpretation of the results, or writing of the paper.Peer reviewedPublisher PD

Cross-sectional and longitudinal associations of neighborhood characteristics with inflammatory markers: findings from the multi-ethnic study of atherosclerosis

We investigated cross-sectional associations of neighborhood deprivation, problems, safety, and cohesion with circulating levels of fibrinogen, interleukin-6, and C-reactive protein (n = 5370) and longitudinal associations with changes in IL-6 over a 3-4 year period (n = 946). In cross-sectional analyses, higher levels of neighborhood deprivation and problems were associated with higher levels of all three inflammatory markers, whereas higher levels of safety were associated with lower levels. Fibrinogen remained associated with all neighborhood characteristics except cohesion and IL-6 remained associated with safety after adjustment for race and SES. In longitudinal analyses, higher levels of neighborhood deprivation and problems, and lower levels of safety were associated with greater longitudinal increases in IL-6 after adjustment for age, sex, race, and SES. These findings were not substantially modified by further risk factor adjustment. Although findings regarding different inflammatory markers were mixed, the longitudinal results that are less limited by race confounding suggest that inflammatory pathways may contribute to neighborhood differences in cardiovascular disease risk.http://deepblue.lib.umich.edu/bitstream/2027.42/78310/1/NazmiDiezRoux2010_HealthPlace.pd

Variations in Hip Shape Are Associated with Radiographic Knee Osteoarthritis : Cross-sectional and Longitudinal Analyses of the Johnston County Osteoarthritis Project

Acknowledgment We thank our funding sources, as well as the staff and participants in the Johnston County Osteoarthritis Project, without whom this work would not be possible. Funding was provided in part by the US National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) K23 AR061406 (Nelson); US National Institutes of Health (NIH)/NIAMS P60AR30701 (Jordan/Renner/Schwartz); US Centers for Disease Control/Association of Schools of Public Health S043 and S3486 (Jordan/Renner); K24-AR04884, P50-AR063043, and P50-AR060752 (Lane); and NIH/National Center for Advancing Translational Sciences KL2TR001109 (Golightly).Peer reviewedPostprin

Dietary patterns, food groups, and telomere length in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND: Telomere length reflects biological aging and may be influenced by environmental factors, including those that affect inflammatory processes. OBJECTIVE: With data from 840 white, black, and Hispanic adults from the Multi-Ethnic Study of Atherosclerosis, we studied cross-sectional associations between telomere length and dietary patterns and foods and beverages that were associated with markers of inflammation. DESIGN: Leukocyte telomere length was measured by quantitative polymerase chain reaction. Length was calculated as the amount of telomeric DNA (T) divided by the amount of a single-copy control DNA (S) (T/S ratio). Intake of whole grains, fruit and vegetables, low-fat dairy, nuts or seeds, nonfried fish, coffee, refined grains, fried foods, red meat, processed meat, and sugar-sweetened soda were computed with responses to a 120-item food-frequency questionnaire completed at baseline. Scores on 2 previously defined empirical dietary patterns were also computed for each participant. RESULTS: After adjustment for age, other demographics, lifestyle factors, and intakes of other foods or beverages, only processed meat intake was associated with telomere length. For every 1 serving/d greater intake of processed meat, the T/S ratio was 0.07 smaller (beta +/- SE: -0.07 +/- 0.03, P = 0.006). Categorical analysis showed that participants consuming >or=1 serving of processed meat each week had 0.017 smaller T/S ratios than did nonconsumers. Other foods or beverages and the 2 dietary patterns were not associated with telomere length. CONCLUSIONS: Processed meat intake showed an expected inverse association with telomere length, but other diet features did not show their expected associations.http://deepblue.lib.umich.edu/bitstream/2027.42/78527/1/NettletonDiezRoux2008_AmJClinNutr.pd

Estrategia de generaci?n de valor en una empresa de distribuci?n el?ctrica

Entre los pa?ses de Latinoam?rica, el Per? ha tenido un gran repunte econ?mico en el 2010. Esto ha ocasionado que el sector el?ctrico peruano se desarrolle en un contexto muy competitivo en cuanto a la generaci?n, y en un contexto regulado respecto a la transmisi?n y distribuci?n, actividades, estas ?ltimas, de caracter?sticas monop?licas. En este mercado exigente est? inmersa Electro Sur Este (ELSE), cuya cobertura de servicio ha crecido en el ?ltimo a?o debido a las pol?ticas nacionales de expansi?n de redes de distribuci?n que, sin duda alguna, ayudaron a facilitar el acceso al fluido el?ctrico a las poblaciones de zonas rurales. Pese a ello, la utilidad de la empresa en el 2010 disminuy? y afect? de manera negativa los ?ndices de rentabilidad econ?mico - financiera. Ante esta situaci?n, el presente estudio propone una estrategia orientada a incrementar la generaci?n de valor econ?mico para los accionistas. La investigaci?n consta de dos etapas. En la primera se revisa el marco conceptual y algunas metodolog?as relacionadas con la generaci?n de valor, principalmente el esquema de factores cr?ticos de ?xito (FCE) en una empresa de distribuci?n el?ctrica. En la segunda etapa se desarrolla una metodolog?a de investigaci?n propia con el objetivo de definir una propuesta de generaci?n de valor para ELSE. Se realiza un an?lisis situacional de la empresa; se identifican y determinan los principales FCE, se hace un benchmarking con exitosas empresas el?ctricas de otros pa?ses de la regi?n y, por ?ltimo, se proyecta un flujo de caja descontado para la evaluaci?n del valor de las actividades y las estrategias propuestas