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Missing covariates

Eun Ji Kim, Yiyang Yuan, Jane Liebschutz, Howard Cabral, Lewis Kazis
BACKGROUND: Disabilities affect more than 1 in 5 US adults, and those with disabilities face multiple barriers in accessing health care. A digital gap, defined as the disparity caused by differences in the ability to use advanced technologies, is assumed to be prevalent among individuals with disabilities. OBJECTIVE: This study examined the associations between disability and use of information technology (IT) in obtaining health information and between trust factors and IT use...
March 16, 2018: JMIR Rehabilitation and Assistive Technologies
Yongjian Xu, Jie Ma, Na Wu, Xiaojing Fan, Tao Zhang, Zhongliang Zhou, Jianmin Gao, Jianping Ren, Gang Chen
INTRODUCTION: In 2009, China officially launched the New Health Care Reform (NHCR). One important purpose of the reform was to reduce financial burden of health care through health insurance expansion and health care provider regulations. This study aimed to provide evidence on the effect of the NHCR reform on catastrophic health expenditure (CHE) by comparing the occurrence and inequality of CHE among households with chronic diseases patients before and after the reform. METHODS: This study used the subset of data from the 2008 and 2013 National Health Services Survey conducted in Shaanxi Province...
2018: PloS One
Ke-Hai Yuan, Mortaza Jamshidian, Yutaka Kano
Unless data are missing completely at random (MCAR), proper methodology is crucial for the analysis of incomplete data. Consequently, methods for effectively testing the MCAR mechanism become important, and procedures were developed via testing the homogeneity of means and variances-covariances across the observed patterns (e.g., Kim & Bentler in Psychometrika 67:609-624, 2002; Little in J Am Stat Assoc 83:1198-1202, 1988). The current article shows that the population counterparts of the sample means and covariances of a given pattern of the observed data depend on the underlying structure that generates the data, and the normal-distribution-based maximum likelihood estimates for different patterns of the observed sample can converge to the same values even when data are missing at random or missing not at random, although the values may not equal those of the underlying population distribution...
March 12, 2018: Psychometrika
Ralph A H Stewart, Dominika Szalewska, Amanda Stebbins, Hussein R Al-Khalidi, John G H Cleland, Andrzej Rynkiewicz, Mark H Drazner, Harvey D White, Daniel B Mark, Ambuj Roy, Dragana Kosevic, Miroslaw Rajda, Marek Jasinski, Chua Yeow Leng, Wiwun Tungsubutra, Patrice Desvigne-Nickens, Eric J Velazquez, Mark C Petrie
Background: In patients with ischaemic left ventricular dysfunction, coronary artery bypass surgery (CABG) may decrease mortality, but it is not known whether CABG improves functional capacity. Objective: To determine whether CABG compared with medical therapy alone (MED) increases 6 min walk distance in patients with ischaemic left ventricular dysfunction and coronary artery disease amenable to revascularisation. Methods: The Surgical Treatment in Ischemic Heart disease trial randomised 1212 patients with ischaemic left ventricular dysfunction to CABG or MED...
2018: Open Heart
Tingting Sha, Wenwei Cheng, Yan Yan
BACKGROUND: Substantial evidence indicates that the relationship between blood pressure (BP) measures and cognitive functioning is inconsistent, complex, and age-related. Pulse pressure (PP), which can not only reflect arterial stiffness and but also represent the chronic effects of hypertension other than BP itself, has been considered as a better predictor of cognitive impairment. However, evidence on the association of cognitive function with PP has not been investigated extensively...
March 12, 2018: Alzheimer's Research & Therapy
Brett K J Kilb, Andrew P Kurmis, Michael Parry, Karen Sherwood, Paul Keown, Bassam A Masri, Clive P Duncan, Donald S Garbuz
BACKGROUND: Once touted as the future of hip arthroplasty, metal-on-metal (MoM) bearing surfaces have fallen sharply from favor with the emergence of a strong body of evidence demonstrating unacceptably high premature implant failure rates. The previously unpredictable development of adverse local tissue reactions (ALTRs) has been a substantive contributor to this. Although the underlying pathophysiology of these so-called "pseudotumors" is now well understood, the fundamental predisposing patient risk factors have remained elusive...
February 2018: Clinical Orthopaedics and related Research
Robin Newhouse, Ha Do Byon, Emily Storkman Wolf, Meg Johantgen
PROBLEM: High-quality smoking cessation counseling guidelines for people who use tobacco are not fully integrated in acute-care services presenting missed opportunities to improve health outcomes. The role of the practice environment on enhancing or inhibiting guideline use is unknown. OBJECTIVE: To examine the relationship between the nurse practice environment and nurses' use of smoking cessation counseling practices, and to evaluate the effect of the individual nurse and organization characteristics on nurse smoking cessation counseling practices...
March 12, 2018: Worldviews on Evidence-based Nursing
Jonathan Ronen, Altuna Akalin
Single cell RNA-seq (scRNA-seq) experiments suffer from a range of characteristic technical biases, such as dropouts (zero or near zero counts) and high variance. Current analysis methods rely on imputing missing values by various means of local averaging or regression, often amplifying biases inherent in the data. We present netSmooth, a network-diffusion based method that uses priors for the covariance structure of gene expression profiles on scRNA-seq experiments in order to smooth expression values. We demonstrate that netSmooth improves clustering results of scRNA-seq experiments from distinct cell populations, time-course experiments, and cancer genomics...
2018: F1000Research
Jahidur Rahman Khan, Md Mazharul Islam, Nabil Awan, Olav Muurlink
BACKGROUND: Low birth weight (LBW) remains a leading global cause of childhood morbidity and mortality. This study leverages a large national survey to determine current prevalence and socioeconomic, demographic and heath related factors associated with LBW in Bangladesh. METHODS: Data from the Multiple Indicator Cluster Survey (MICS) 2012-13 of Bangladesh were analyzed. A total of 2319 women for whom contemporaneous birth weight data was available and who had a live birth in the two years preceding the survey were sampled for this study...
March 6, 2018: BMC Pediatrics
Shijia Zhu, Gang Fang
Motivation: For many traits, causal loci uncovered by genetic-mapping studies explain only a minority of the heritable contribution to trait variation. Multiple explanations for this 'missing heritability' have been proposed. SNP-SNP interaction (epistasis), as one of the compelling models, has been widely studied. However, the genome-wide scan of epistasis, especially for quantitative traits, poses huge computational challenges. Moreover, covariate adjustment is largely ignored in epistasis analysis due to the massive extra computational undertaking...
March 2, 2018: Bioinformatics
Elizabeth Ojukwu, Lauren R Powell, Sharina D Person, Milagros C Rosal, Stephenie C Lemon, Jeroan Allison
African Americans remain underrepresented in health-related research. We examined the association between spirituality using the Self-Rating Spirituality Scale (range 6-24) and self-reported willingness to participate in health-related research studies among African Americans. Covariates included gender, education level, employment status, and previous research experience. Adjusted associations were calculated with logistic regression models, with multiple imputation to account for missing data. Results from the logistic regression model show that each one-point increase in the Self-Rating Spirituality Scale was associated with a 24% increase in the odds of being very likely to participate in research (OR: 1...
2018: Journal of Health Care for the Poor and Underserved
Dania Daye, Emmanuel Carrodeguas, McKinley Glover, Claude Emmanuel Guerrier, H Benjamin Harvey, Efrén J Flores
PURPOSE: The aim of this study was to investigate the impact of wait days (WDs) on missed outpatient MRI appointments across different demographic and socioeconomic factors. METHODS: An institutional review board-approved retrospective study was conducted among adult patients scheduled for outpatient MRI during a 12-month period. Scheduling data and demographic information were obtained. Imaging missed appointments were defined as missed scheduled imaging encounters...
March 1, 2018: Journal of the American College of Radiology: JACR
Aline Macarevich, Luciane Maria Pilotto, Juliana Balbinot Hilgert, Roger Keller Celeste
This article aimed to describe the levels of user satisfaction in different age groups and to study the association between user satisfaction and different types of dental services in a representative sample of Brazilians. This study is based on the Brazilian Oral Health Survey, which evaluated the dental health of adolescents, adults and older adults in 177 Brazilian cities. The outcome variable was user satisfaction, related to the last dental visit, evaluated in a five-level Likert-type scale. The main exposure variable was the type of dental service (public service, private service, health plan or insurance)...
February 19, 2018: Cadernos de Saúde Pública
Yanqing Sun, Li Qi, Guangren Yang, Peter B Gilbert
This article develops hypothesis testing procedures for the stratified mark-specific proportional hazards model with missing covariates where the baseline functions may vary with strata. The mark-specific proportional hazards model has been studied to evaluate mark-specific relative risks where the mark is the genetic distance of an infecting HIV sequence to an HIV sequence represented inside the vaccine. This research is motivated by analyzing the RV144 phase 3 HIV vaccine efficacy trial, to understand associations of immune response biomarkers on the mark-specific hazard of HIV infection, where the biomarkers are sampled via a two-phase sampling nested case-control design...
February 28, 2018: Biometrical Journal. Biometrische Zeitschrift
Ai Rene Ong, Mengyao Hu, Brady T West, John A Kirlin
OBJECTIVE: To understand the effects of interviewers on the responses they collect for measures of food security, income and selected survey quality measures (i.e. discrepancy between reported Supplemental Nutrition Assistance Program (SNAP) status and administrative data, length of time between initial and final interview, and missing income data) in the US Department of Agriculture's National Household Food Acquisition and Purchase Survey (FoodAPS). DESIGN: Using data from FoodAPS, multilevel models with random interviewer effects were fitted to estimate the variance in each outcome measure arising from effects of the interviewers...
February 22, 2018: Public Health Nutrition
Lars Skou Elkjær, Bodil Hammer Bech, Yuelian Sun, Thomas Munk Laursen, Jakob Christensen
Importance: Valproate sodium is used for the treatment of epilepsy and other neuropsychiatric disorders in women of childbearing potential. However, there are concerns about impaired cognitive development in children who have been exposed to valproate during pregnancy. Objective: To estimate the association between long-term school performance and prenatal exposure to valproate and a number of other antiepileptic drugs (AEDs). Design, Setting, and Participants: In a prospective, population-based cohort study conducted from August 1, 2015, to May 31, 2017, data used in the study were provided by Statistics Denmark on April 15, 2016...
February 19, 2018: JAMA Neurology
John W Jackson, Ian Schmid, Elizabeth A Stuart
Purpose of review: Propensity score methods have become commonplace in pharmacoepidemiology over the past decade. Their adoption has confronted formidable obstacles that arise from pharmacoepidemiology's reliance on large healthcare databases of considerable heterogeneity and complexity. These include identifying clinically meaningful samples, defining treatment comparisons, and measuring covariates in ways that respect sound epidemiologic study design. Additional complexities involve correctly modeling treatment decisions in the face of variation in healthcare practice, and dealing with missing information and unmeasured confounding...
December 2017: Current Epidemiology Reports
Faisal M Zahid, Christian Heumann
Missing data is a common issue that can cause problems in estimation and inference in biomedical, epidemiological and social research. Multiple imputation is an increasingly popular approach for handling missing data. In case of a large number of covariates with missing data, existing multiple imputation software packages may not work properly and often produce errors. We propose a multiple imputation algorithm called mispr based on sequential penalized regression models. Each variable with missing values is assumed to have a different distributional form and is imputed with its own imputation model using the ridge penalty...
January 1, 2018: Statistical Methods in Medical Research
Steven Novick, Perceval Sondag, Tim Schofield, Kenneth Miller
For biotherapeutics and vaccines, potency is measured in a bioassay which compares the concentration-response curves of a new batch to that of a reference standard. Acceptable accuracy and precision of potency measurement is critical to the manufacturing of these products. These characteristics of a bioassay are typically assessed in a procedure which is carried out with samples spanning the acceptable range for the product. During early development, however, a full validation study such as that which is carried out in late development can be costly as it relates to the likelihood of eventual program success...
February 14, 2018: PDA Journal of Pharmaceutical Science and Technology
Alexandra A N'Goran, Jérôme Pasquier, Anouk Deruaz-Luyet, Bernard Burnand, Dagmar M Haller, Stefan Neuner-Jehle, Andreas Zeller, Sven Streit, Lilli Herzig, Patrick Bodenmann
OBJECTIVE: To identify factors associated with health literacy in multimorbid patients. DESIGN: A nationwide cross-sectional study in Switzerland. Univariate and multivariate linear regressions were calculated to identify variables associated with health literacy. A multiple imputation approach was used to deal with missing values. PARTICIPANTS: Multimorbid patients recruited in primary care settings (n=888), above 18 years old and suffering from at least 3 of 75 chronic conditions on a predefined list based on the International Classification of Primary Care 2...
February 13, 2018: BMJ Open
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