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Regression Modeling (regression + modeling)
Kinds of Regression Modeling Selected AbstractsApplied Survival Analysis: Regression Modeling of Time-to-Event Data, 2nd edition by HOSMER, D. W., LEMESHOW, S., and MAY, S.BIOMETRICS, Issue 2 2009Article first published online: 28 MAY 200 No abstract is available for this article. [source] Gaussian Process Functional Regression Modeling for Batch DataBIOMETRICS, Issue 3 2007J. Q. Shi Summary A Gaussian process functional regression model is proposed for the analysis of batch data. Covariance structure and mean structure are considered simultaneously, with the covariance structure modeled by a Gaussian process regression model and the mean structure modeled by a functional regression model. The model allows the inclusion of covariates in both the covariance structure and the mean structure. It models the nonlinear relationship between a functional output variable and a set of functional and nonfunctional covariates. Several applications and simulation studies are reported and show that the method provides very good results for curve fitting and prediction. [source] Semiparametric Regression Modeling with Mixtures of Berkson and Classical Error, with Application to Fallout from the Nevada Test SiteBIOMETRICS, Issue 1 2002Bani Mallick Summary. We construct Bayesian methods for semiparametric modeling of a monotonic regression function when the predictors are measured with classical error, Berkson error, or a mixture of the two. Such methods require a distribution for the unobserved (latent) predictor, a distribution we also model semi-parametrically. Such combinations of semiparametric methods for the dose-response as well as the latent variable distribution have not been considered in the measurement error literature for any form of measurement error. In addition, our methods represent a new approach to those problems where the measurement error combines Berkson and classical components. While the methods are general, we develop them around a specific application, namely, the study of thyroid disease in relation to radiation fallout from the Nevada test site. We use this data to illustrate our methods, which suggest a point estimate (posterior mean) of relative risk at high doses nearly double that of previous analyses but that also suggest much greater uncertainty in the relative risk. [source] Predicting Hospital Admission and Returns to the Emergency Department for Elderly PatientsACADEMIC EMERGENCY MEDICINE, Issue 3 2010Michael A. LaMantia MD Abstract Objectives:, Methods to accurately identify elderly patients with a high likelihood of hospital admission or subsequent return to the emergency department (ED) might facilitate the development of interventions to expedite the admission process, improve patient care, and reduce overcrowding. This study sought to identify variables found among elderly ED patients that could predict either hospital admission or return to the ED. Methods:, All visits by patients 75 years of age or older during 2007 at an academic ED serving a large community of elderly were reviewed. Clinical and demographic data were used to construct regression models to predict admission or ED return. These models were then validated in a second group of patients 75 and older who presented during two 1-month periods in 2008. Results:, Of 4,873 visits, 3,188 resulted in admission (65.4%). Regression modeling identified five variables statistically related to the probability of admission: age, triage score, heart rate, diastolic blood pressure, and chief complaint. Upon validation, the c-statistic of the receiver operating characteristic (ROC) curve was 0.73, moderately predictive of admission. We were unable to produce models that predicted ED return for these elderly patients. Conclusions:, A derived and validated triage-based model is presented that provides a moderately accurate probability of hospital admission of elderly patients. If validated experimentally, this model might expedite the admission process for elderly ED patients. Our models failed, as have others, to accurately predict ED return among elderly patients, underscoring the challenge of identifying those individuals at risk for early ED returns. ACADEMIC EMERGENCY MEDICINE 2010; 17:252,259 © 2010 by the Society for Academic Emergency Medicine [source] Gray matter atrophy is related to long-term disability in multiple sclerosisANNALS OF NEUROLOGY, Issue 3 2008Leonora K. Fisniku MRCP Objective To determine the relation of gray matter (GM) and white matter (WM) brain volumes, and WM lesion load, with clinical outcomes 20 years after first presentation with clinically isolated syndrome suggestive of multiple sclerosis (MS). Methods Seventy-three patients were studied a mean of 20 years from first presentation with a clinically isolated syndrome (33 of whom developed relapsing-remitting MS and 11 secondary-progressive MS, with the rest experiencing no further definite neurological events), together with 25 healthy control subjects. GM and WM volumetric measures were obtained from three-dimensional T1-weighted brain magnetic resonance images using Statistical Parametric Mapping 2. Results Significant GM (p < 0.001) and WM atrophy (p = 0.001) was seen in MS patients compared with control subjects. There was significantly more GM, but not WM atrophy, in secondary-progressive MS versus relapsing-remitting MS (p = 0.003), and relapsing-remitting MS versus clinically isolated syndrome (p < 0.001). GM, but not WM, fraction correlated with expanded disability status scale (rs = ,0.48; p < 0.001) and MS Functional Composite scores (rs = 0.59; p < 0.001). WM lesion load correlated with GM (rs = ,0.63; p < 0.001), but not with WM fraction. Regression modeling indicated that the GM fraction explained more of the variability in clinical measures than did WM lesion load. Interpretation In MS patients with a relatively long and homogeneous disease duration, GM atrophy is more marked than WM atrophy, and reflects disease subtype and disability to a greater extent than WM atrophy or lesions. Ann Neurol 2008 [source] Prognostic factors and outcome of recurrence in childhood acute myeloid leukemia,CANCER, Issue 1 2007Jeffrey E. Rubnitz MD Abstract BACKGROUND. Outcome after recurrence of childhood acute myeloid leukemia (AML) is poor. We performed this study to identify prognostic factors for recurrence and for survival after recurrence of AML. METHODS. The clinical characteristics, biological features, treatment modalities, and outcomes of children with de novo AML who were enrolled on 3 consecutive clinical protocols from 1987 to 2002 at St. Jude Children's Research Hospital were studied. Regression modeling was used to identify prognostic factors for recurrence and for survival after recurrence. RESULTS. The outcome after recurrence was poor, with a 5-year survival estimate of only 23.3% ± 5.7%. Multivariable analysis indicated that male sex (P = .005), autologous stem cell transplant before recurrence (P = .097), each additional month from diagnosis to recurrence (P = .041), and stem cell transplant after recurrence (P < .001) were associated with a better survival after recurrence, whereas M5 or M7 morphology (P = .001) were significantly predictive of a lower survival estimate after recurrence. CONCLUSIONS. Survival after recurrence was poor in children with AML. Novel therapies are urgently needed to prevent or to treat recurring AML. Cancer 2007. © 2006 American Cancer Society. [source] Home-based therapy with ready-to-use therapeutic food is of benefit to malnourished, HIV-infected Malawian childrenACTA PAEDIATRICA, Issue 2 2005MJ Ndekha Abstract Aim: To determine if home-based nutritional therapy will benefit a significant fraction of malnourished, HIV-infected Malawian children, and to determine if ready-to-use therapeutic food (RUTF) is more effective in home-based nutritional therapy than traditional foods. Methods: 93 HIV-positive children >1 y old discharged from the nutrition unit in Blantyre, Malawi were systematically allocated to one of three dietary regimens: RUTF, RUTF supplement or blended maize/soy flour. RUTF and maize/soy flour provided 730 kJ·kg,1·d,1, while the RUTF supplement provided a fixed amount of energy, 2100 kJ/d. These children did not receive antiretroviral chemotherapy. Children were followed fortnightly. Children completed the study when they reached 100% weight-for-height, relapsed or died. Outcomes were compared using regression modeling to account for differences in the severity of malnutrition between the dietary groups. Results: 52/93 (56%) of all children reached 100% weight-for-height. Regression modeling found that the children receiving RUTF gained weight more rapidly and were more likely to reach 100% weight-for-height than the other two dietary groups (p<0.05). Conclusion: More than half of malnourished, HIV-infected children not receiving antiretroviral chemotherapy benefit from home-based nutritional rehabilitation. Home-based therapy RUTF is associated with more rapid weight gain and a higher likelihood of reaching 100% weight-for-height. [source] An investigation of computer literacy and attitudes amongst Greek post-graduate dental studentsEUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 3 2007Kimon Divaris An accurate assessment of the computer skills of students is a pre-requisite for the success of any e-learning interventions. The aim of the present study was to assess objectively the computer literacy and attitudes in a group of Greek post-graduate students, using a task-oriented questionnaire developed and validated in the University of Malmö, Sweden. 50 post-graduate students in the Athens University School of Dentistry in April 2005 took part in the study. A total competence score of 0,49 was calculated. Socio-demographic characteristics were recorded. Attitudes towards computer use were assessed. Descriptive statistics and linear regression modeling were employed for data analysis. Total competence score was normally distributed (Shapiro,Wilk test: W = 0.99, V = 0.40, P = 0.97) and ranged from 5 to 42.5, with a mean of 22.6 (±8.4). Multivariate analysis revealed ,gender', ,e-mail ownership' and ,enrollment in non-clinical programs' as significant predictors of computer literacy. Conclusively, computer literacy of Greek post-graduate dental students was increased amongst males, students in non-clinical programs and those with more positive attitudes towards the implementation of computer assisted learning. [source] Linkage mapping methods applied to the COGA data set: Presentation Group 4 of Genetic Analysis Workshop 14GENETIC EPIDEMIOLOGY, Issue S1 2005E. Warwick Daw Abstract Presentation Group 4 participants analyzed the Collaborative Study on the Genetics of Alcoholism data provided for Genetic Analysis Workshop 14. This group examined various aspects of linkage analysis and related issues. Seven papers included linkage analyses, while the eighth calculated identity-by-descent (IBD) probabilities. Six papers analyzed linkage to an alcoholism phenotype: ALDX1 (four papers), ALDX2 (one paper), or a combination both (one paper). Methods used included Bayesian variable selection coupled with Haseman-Elston regression, recursive partitioning to identify phenotype and covariate groupings that interact with evidence for linkage, nonparametric linkage regression modeling, affected sib-pair linkage analysis with discordant sib-pair controls, simulation-based homozygosity mapping in a single pedigree, and application of a propensity score to collapse covariates in a general conditional logistic model. Alcoholism linkage was found with ,2 of these approaches on chromosomes 2, 4, 6, 7, 9, 14, and 21. The remaining linkage paper compared the utility of several single-nucleotide polymorphism (SNP) and microsatellite marker maps for Monte Carlo Markov chain combined oligogenic segregation and linkage analysis, and analyzed one of the electrophysiological endophenotypes, ttth1, on chromosome 7. Linkage was found with all marker sets. The last paper compared the multipoint IBD information content of several SNP sets and the microsatellite set, and found that while all SNP sets examined contained more information than the microsatellite set, most of the information contained in the SNP sets was captured by a subset of the SNP markers with ,1-cM marker spacing. From these papers, we highlight three points: a 1-cM SNP map seems to capture most of the linkage information, so denser maps do not appear necessary; careful and appropriate use of covariates can aid linkage analysis; and sources of increased gene-sharing between relatives should be accounted for in analyses. Genet. Epidemiol. 29(Suppl. 1):S29,S34, 2005. © 2005 Wiley-Liss, Inc. [source] The Impact of Metropolitan Structure on Commute Behavior in the Netherlands: A Multilevel ApproachGROWTH AND CHANGE, Issue 3 2004Tim Schwanen ABSTRACT This paper documents the investigation of the impact of metropolitan structure on the commute behavior of urban residents in the Netherlands. Not only has the impact of monocentrism versus polycentrism been analyzed, but the influence of metropolitan density and size has also been considered, together with the ratio of employment to population and the growth of the population and employment. Furthermore, data are used at a variety of levels of analysis ranging from the individual worker to the metropolitan region rather than being drawn from aggregate level statistics alone. Multilevel regression modeling is applied to take account of the interdependencies among these levels of aggregation. With regard to mode choice, the results indicate that the probability of driving an auto to work is lower in employment-rich metropolitan regions, and rises as the number of jobs per resident has grown strongly. Furthermore, women in most polycentric regions are less likely to commute as an auto driver. All else being equal, commute distances and times for auto drivers are longer in most polycentric regions than in monocentric urban areas. In addition, commute time as an auto driver rises with metropolitan size, whereas commute distance depends on employment density and the growth of the number of jobs per resident. The investigation shows that metropolitan structure, although significantly influencing commute patterns, explains only a small part of the variation of individuals' commute behavior. [source] Effects of the introduction of the German "Praxisgebühr" on outpatient care and treatment of patients with atopic eczemaJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 10 2009Jochen Schmitt Summary Background: The introduction of a co-payment of 10 Euros per quarter and physician for adults (the so called "Praxisgebühr") as of January 01, 2004 was a significant health policy measure with unknown effects on medical care of patients with atopic eczema (AE). Methods: Analysis of an administrative healthcare database from Saxony, Germany. Comparison of outpatient care and treatment of 11,036 patients with AE (6,696 adults) in the year before (2003) and after (2004) the introduction of the co-payment using descriptive statistics and logistic regression modeling. Results: The proportion of adults with AE treated by dermatologists decreased from 52.8% in 2003 to 42.3% in the year after the co-payment was introduced. Consultations of general practitioners by adults and health services utilization by children/adolescents did not change. Treatment with topical calcineurin inhibitors in 2003 was an independent predictor for re-consultation in 2004 (p < 0.001). The proportion of adults receiving systemic steroids for AE significantly increased in 2004 (males: 2003: 5.9%, 2004:10.3%, p < 0.001; females: 2003: 5.7%, 2004: 8.2%, p < 0.001). The risk for treatment with systemic steroids increased with the decrease in consulting frequency due to AE relative to 2003 (p = 0.006). Conclusions: After the introduction of the German "Praxisgebühr" fewer patients with AE received dermatological treatment. Simultaneously, an unexpectedly significant increase in the (non evidence-based) treatment of AE with systemic steroids was observed, of which patients with relatively lower consultation frequency after the introduction of the co-payment were particularly affected. [source] Carbonated Soft Drink Consumption and Bone Mineral Density in Adolescence: The Northern Ireland Young Hearts Project,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2003C McGartland Abstract In an observational study of 1335 boys and girls aged 12 and 15 years, higher intakes of carbonated soft drinks (CSDs) were significantly associated with lower bone mineral density at the heel, but only in girls. Owing to the upward trend in CSD intake in adolescence, this finding may be of concern. Introduction: High consumption of carbonated soft drinks (CSD) during adolescence may reduce bone mineral accrual and increase fracture risk. The aim of this study was to examine the relationship between CSD consumption and bone mineral density (BMD) in a representative sample of adolescents. Materials and Methods: This was a cross-sectional observational study in 36 postprimary schools in Northern Ireland. Participants included 591 boys and 744 girls either 12 or 15 years old. BMD was measured by DXA, and usual beverage consumption was assessed by the diet history method. Adjusted regression modeling was used to investigate the influence of CSD on BMD. Results: A significant inverse relationship between total CSD intake and BMD was observed in girls at the dominant heel (,, ,0.099; 95% CI, ,0.173 to ,0.025). Non-cola consumption was inversely associated with dominant heel BMD in girls (,, ,0.121; 95% CI, ,0.194 to ,0.048), and diet drinks were also inversely associated with heel BMD in girls (,, ,0.087; 95% CI, ,0.158 to ,0.016). However, no consistent relationships were observed between CSD intake and BMD in boys. Cola consumption and nondiet drinks were not significantly related to BMD in either sex. Conclusion: CSD consumption seems to be inversely related to BMD at the dominant heel in girls. It is possible that the apparent association results from the displacement of more nutritious beverages from the diet. Although the inverse association observed between CSD consumption and BMD is modest and confined to girls, this finding may have important public health implications given the widespread use and current upward trend in CSD consumption in Western populations. [source] Body mass index (BMI) and risk of noncardiac postoperative medical complications in elderly hip fracture patients: A population-based study,,JOURNAL OF HOSPITAL MEDICINE, Issue 8 2009John A. Batsis MD Abstract BACKGROUND: Obese patients are thought to be at higher risk of postoperative medical complications. We determined whether body mass index (BMI) is associated with postoperative in-hospital noncardiac complications following urgent hip fracture repair. METHODS: We conducted a population-based study of Olmsted County, Minnesota, residents operated on for hip fracture in 1988 to 2002. BMI was categorized as underweight (<18.5 kg/m2), normal (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), and obese (,30 kg/m2). Postoperative inpatient noncardiac medical complications were assessed. Complication rates were estimated for each BMI category and overall rates were assessed using logistic regression modeling. RESULTS: There were 184 (15.6%) underweight, 640 (54.2%) normal, 251 (21.3%) overweight, and 105 (8.9%) obese hip fracture repairs (mean age, 84.2 ± 7.5 years; 80% female). After adjustment, the risk of developing an inpatient noncardiac complication for each BMI category, compared to normal BMI, was: underweight (odds ratio [OR], 1.33; 95% confidence interval [CI], 0.95-1.88; P = 0.10), overweight (OR, 1.01; 95% CI, 0.74-1.38; P = 0.95), and obese (OR, 1.28; 95% CI, 0.82-1.98; P = 0.27). Multivariate analysis demonstrated that an ASA status of III-V vs. I-II (OR, 1.84; 95% CI, 1.25-2.71; P = 0.002), a history of chronic obstructive pulmonary disease (COPD) or asthma (OR, 1.58; 95% CI, 1.18-2.12; P = 0.002), male sex (OR, 1.49; 95% CI, 1.10-2.02; P = 0.01), and older age (OR, 1.05; 95% CI, 1.03-1.06; P < 0.001) contributed to an increased risk of developing a postoperative noncardiac inpatient complication. Underweight patients had higher in-hospital mortality rates than normal BMI patients (9.3 vs. 4.4%; P = 0.01). CONCLUSIONS: BMI has no significant influence on postoperative noncardiac medical complications in hip-fracture patients. These results attenuate concerns that obese or frail, underweight hip-fracture patients may be at higher risk postoperatively for inpatient complications. Journal of Hospital Medicine 2009;4:E1,E9. © 2009 Society of Hospital Medicine. [source] An improved independent component regression modeling and quantitative calibration procedureAICHE JOURNAL, Issue 6 2010Chunhui Zhao Abstract An improved independent component regression (M-ICR) algorithm is proposed by constructing joint latent variable (LV) based regressors, and a quantitative statistical analysis procedure is designed using a bootstrap technique for model validation and performance evaluation. First, the drawbacks of the conventional regression modeling algorithms are analyzed. Then the proposed M-ICR algorithm is formulated for regressor design. It constructs a dual-objective optimization criterion function, simultaneously incorporating quality-relevance and independence into the feature extraction procedure. This ties together the ideas of partial-least squares (PLS), and independent component regression (ICR) under the same mathematical umbrella. By adjusting the controllable suboptimization objective weights, it adds insight into the different roles of quality-relevant and independent characteristics in calibration modeling, and, thus, provides possibilities to combine the advantages of PLS and ICR. Furthermore, a quantitative statistical analysis procedure based on a bootstrapping technique is designed to identify the effects of LVs, determine a better model rank and overcome ill-conditioning caused by model over-parameterization. A confidence interval on quality prediction is also approximated. The performance of the proposed method is demonstrated using both numerical and real world data. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Varicella susceptibility and vaccine use among young adults enlisting in the United States Navy,,JOURNAL OF MEDICAL VIROLOGY, Issue S1 2003Margaret A.K. Ryan Abstract Primary varicella infection, or chicken pox, is a threat to all young adults who join the United States (U.S.) military if they fail to develop immunity prior to enlistment. Historically, outbreaks of chicken pox have caused marked morbidity and impaired military readiness. In December 1996, the U.S. Navy began performing serologic testing for varicella among all new recruits, and vaccinating those found to be sero-negative. We evaluated results of the screening program in its first 4 years, and used multivariable logistic regression modeling to describe factors associated with varicella susceptibility. Cases of chicken pox were tracked among all military services before and after program implementation. More than 190,000 young adults enlisted in the U.S. Navy between 1997 and 2000. Recruits originated from all 50 states and several foreign countries; 84% were male, and their average age was 19 years. Seven percent were found to be susceptible (sero-negative) to varicella. In multivariable modeling, race/ethnicity was associated with susceptibility, but age, gender, and home state were not. The overall incidence of chicken pox in the Navy was reduced by more than 80% after initiation of the screening-vaccination program. A successful varicella screening-vaccination program has been implemented in the U.S. Navy. Results of serologic screening undertaken on this large number of young adults may be useful in tracking the changing epidemiology of varicella in the general population in the post-vaccine era. J. Med. Virol. 70:S15,S19, 2003. © 2003 Wiley-Liss, Inc. [source] Exposure of mouse preosteoblasts to pulsed electromagnetic fields reduces the amount of mature, type I collagen in the extracellular matrixJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2006Yoshitada Sakai Abstract We tested the hypothesis that exposure of a mouse preosteoblast cell line to pulsed electromagnetic fields (PEMF) would affect components of the extracellular matrix. We report that exposure of MC3T3-E1 cells to a single PEMF waveform significantly reduced the amount of mature, ,1(I) collagen in the extracellular matrix (ECM) and the conditioned medium, without affecting the amount of total ECM protein. This decrease was not due to changes in the steady-state level of Col1A1 mRNA or to degradation of mature collagen. We then tested the effect of three distinct PEMF waveforms, two orthogonal coil orientations, and two waveform amplitude levels on the amount of ,1(I) collagen in the conditioned medium. A sequence of factorial ANOVAs and stepwise regression modeling revealed that the period (duration) of the individual pulses accounted for a significant proportion of the variance associated with the amount of ,1(I) collagen in the conditioned medium. The total variance accounted for, however, was small (R2,=,0.155, p,<,0.001 and R2,=,0.172, p,<,0.001, in the horizontal and vertical orientations, respectively). The positive and negative regression coefficients for the coil orientations revealed that the influence of pulse period was significantly different for the orthogonal coil orientations (p,<,0.001). The findings imply that the dominant influence of PEMF on the amount of mature, ,1(I) collagen in the ECM is related to variables other than those expressed in the time-amplitude domain. The results provide objective direction toward identifying waveform characteristics that contribute to the observed between-waveform differences with regard to collagen. Advances in this area may lead toward improving waveforms and waveform delivery protocols. © 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Water Consumption and Nursing Characteristics of Infants by Race and EthnicityJOURNAL OF PUBLIC HEALTH DENTISTRY, Issue 3 2000Keith E. Heller DDS Abstract Objective: The purpose of this project was to determine racial/ethnic differences in water consumption levels and nursing habits of children younger than 2 years old. Methods: Data from the 1994,96 Continuing Survey of Food Intakes by Individuals (CSFII) were used for these analyses. Water consumption and breast-feeding data on 946 children younger than 2 years old were used. Results: For black non-Hispanic children younger than 2 years old (n=121), 5.3 percent of the children were currently being breast fed. This percentage was less than that seen in other racial/ethnic groups. For white non-Hispanic children (n=620), this percentage was 10.8 percent; for Hispanic children (n=146), 12.2 percent; for "other" children, 18.5 percent (n=59). Black non-Hispanic children had the highest total water consumption (128.6 ml/kg/day) among all groups, white non-Hispanic had the lowest (113.2 ml/kg/day). These differences were not statistically significant in multivariate regression modeling. Black non-Hispanic children also drank moretap water (21.3 ml/kg/day) than white non-Hispanic children (12.7 ml/kg/day) and Hispanic children (14.9 ml/kg/day). The difference was statistically significant in multivariate regression modeling. Conclusions: The differences in breast feeding and water consumption observed among black children younger than 2 years of age could be a factor in the observed higher levels of fluorosis in black children compared to other children. [source] Determinants of Lesion Sizes and Tissue Temperatures During Catheter CryoablationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2007MARK A. WOOD M.D. Background:Factors which influence lesion size from catheter-based cryoablation have not been well described. This study describes factors which influence lesion size during catheter cryoablation. Methods and Results:Cryoablation was delivered to porcine left ventricular myocardium in a saline bath using 4- or 8-mm electrode catheters. Ablation was delivered with the electrodes either vertical or horizontal to the tissue and both with and without superfusate flow over the electrode. The effect of electrode contact pressure was tested. Lesion dimensions were measured. All experiments were duplicated to measure tissue temperatures at 1-, 2-, 3-, and 5-mm deep to the ablation electrode. The 8-mm electrode produced lower tissue temperatures and larger lesion volumes when compared with the 4-mm electrode (all P < 0.05). Superfusate flow slowed the rate of tissue cooling, markedly warmed tissue temperatures, and reduced lesion volume when compared with no flow conditions. By linear regression modeling, lesion sizes and tissue temperatures were related to the presence of superfusate flow, electrode orientation, contact pressure and electrode size, or catheter refrigerant flow rate (r2 for models = 0.90,0.96, all P < 0.001). Electrode temperature predicted lesion size or tissue temperatures only when analyzed independent of electrode size or refrigerant flow rate. Conclusions:Lesion sizes and tissue temperatures during catheter cryoablation are related to convective warming, electrode orientation, electrode contact pressure, and any of the following: electrode size, catheter refrigerant flow rate or electrode temperature. However, electrode temperature may be a poor predictor of lesion size and tissue temperature for a given catheter size. [source] The correlates and influences of career-related continuous learning: Implications for management professionalsPERFORMANCE IMPROVEMENT QUARTERLY, Issue 4 2010Kevin D. Kuznia Management personnel are increasingly aware that career success depends on the ability to continuously learn and adapt to the environment. However, scant attention has been paid to how learning activities contribute to managerial success. This study examines the degree to which involvement in career-related continuous learning affects managerial career success. Career success as defined in this study comprises both objective (ascendancy) and subjective (organizational commitment, professional commitment, career satisfaction) elements. Five hypotheses are tested using linear regression modeling. Results indicate that as individuals increase participation in career-related continuous learning, their managerial career success increases as well. [source] Noninvasive assessment of energy expenditure in childrenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2006Isabelle Sarton-Miller This study establishes an affordable, simple, and noninvasive method to assess energy expenditure (EE) in children, an underrepresented group. The method is based on regression modeling, where prediction of oxygen consumption (VO2), a proxy of EE, was deduced from heart rate (HR) and several variables that adjusted for interindividual variability. Limb activities (arms vs. legs) and posture (sitting vs. standing) were represented in the regression as dichotomous covariates. The order of activities and intensities was randomized. Seventy-four children (aged 7,10 years), raised at sea-level (Seattle, WA), comprised the sample. Anthropometric measures were taken, and VO2 and HR were measured for activities using the arms in sitting and standing positions (mixing and punching), as well as walking at different velocities on a treadmill. Repeated measures and least square regression estimation were used. HR, body mass, number of hours of physical activity per week (HPA), an interaction term between sitting and standing resting HR, and the two dichotomous variables, sex and limbs, were significant covariates; posture was not. Several equations were developed for various field uses. The equations were built from sea-level data, but ultimately this method could serve as a baseline for developing a similar approach in other populations, where noninvasive estimation of EE is imperative in order to gain a better understanding of children's energetic issues. Am. J. Hum. Biol. 18:600,609, 2006. © 2006 Wiley-Liss, Inc. [source] Nurse burnout and quality of care: Cross-national investigation in six countries,RESEARCH IN NURSING & HEALTH, Issue 4 2010Lusine Poghosyan Abstract We explored the relationship between nurse burnout and ratings of quality of care in 53,846 nurses from six countries. In this secondary analysis, we used data from the International Hospital Outcomes Study; data were collected from 1998 to 2005. The Maslach Burnout Inventory and a single-item reflecting nurse-rated quality of care were used in multiple logistic regression modeling to investigate the association between nurse burnout and nurse-rated quality of care. Across countries, higher levels of burnout were associated with lower ratings of the quality of care independent of nurses' ratings of practice environments. These findings suggest that reducing nurse burnout may be an effective strategy for improving nurse-rated quality of care in hospitals. © 2010 Wiley Periodicals, Inc. Res Nurs Health 33:288,298, 2010 [source] Secular Trends in the Incidence of Female Breast Cancer in the United States, 1973,1998THE BREAST JOURNAL, Issue 2 2004Kiumarss Nasseri DVM Abstract: , Statistical modeling suggests a causal association between the rapid increase in the incidence of female breast cancer (FBC) in the United States and the widespread use of screening mammography. Additional support for this suggestion is a shift in the stage at diagnosis that consists of an increase in early stage diagnosis followed by a decrease in late-stage diagnosis. This has not been reported in the United States. The objective of this study was to examine the secular trends in the incidence of FBC in search of empirical support for this shift. FBC cases in the Surveillance, Epidemiology, and End Results (SEER) database from 1973 through 1998 were dichotomized into early and late detection based. Early detection included all the in situ and invasive cases with local spread. Late detection included cases with regional spread and distant metastasis. Joinpoint segmented regression modeling was used for trend analysis. Early detection in white and black women followed a similar pattern of significant increase in the early 1980s that continued through 1998 with slight modification in 1987. The expected shift in stage was noticed only for white women when the incidence of late detection in them began to decline in 1987. The incidence of late detection in black women has remained stable. These results provide further support for the previously implied causal association between the use of screening mammography and the increased incidence of FBC in the United States. It also shows that the expected stage shift appeared in white women 50,69 years of age after an estimated detection lead time (DLT) of about 5 years. This is the first estimate of DLT in the United States that is based on actual data. The subsequent increase in late detection in white women since 1993 may be due to changes in case management and the increased use of sentinel lymph node biopsy (SLNB) rather than changes in the etiology or biology of FBC., [source] Rural,Urban Differences in Primary Care Physicians' Practice Patterns, Characteristics, and IncomesTHE JOURNAL OF RURAL HEALTH, Issue 2 2008William B. Weeks MD ABSTRACT:,Context:Low salaries and difficult work conditions are perceived as a major barrier to the recruitment of primary care physicians to rural settings. Purpose: To examine rural,urban differences in physician work effort, physician characteristics, and practice characteristics, and to determine whether, after adjusting for any observed differences, rural primary care physicians' incomes were lower than those of urban primary care physicians. Methods: Using survey data from actively practicing office-based general practitioners (1,157), family physicians (1,378), general internists (2,811), or pediatricians (1,752) who responded to the American Medical Association's annual survey of physicians between 1992 and 2002, we used linear regression modeling to determine the association between practicing in a rural (nonmetropolitan) or urban (standard metropolitan statistical area) setting and physicians' annual incomes after controlling for specialty, work effort, provider characteristics, and practice characteristics. Findings: Rural primary care physicians' unadjusted annual incomes were similar to their urban counterparts, but they tended to work longer hours, complete more patient visits, and have a much greater proportion of Medicaid patients. After adjusting for work effort, physician characteristics, and practice characteristics, primary care physicians who practiced in rural settings made $9,585 (5%) less than their urban counterparts (95% confidence intervals: ,$14,569, ,$4,602, P < .001). In particular, rural practicing general internists and pediatricians experienced lower incomes than did their urban counterparts. Conclusions: Addressing rural physicians' lower incomes, longer work hours, and greater dependence on Medicaid reimbursement may improve the ability to ensure that an adequate supply of primary care physicians practice in rural settings. [source] Analytical approaches for transplant research, 2004AMERICAN JOURNAL OF TRANSPLANTATION, Issue 4p2 2005Douglas E. Schaubel This article provides detailed explanations of the methods frequently employed in outcomes analyses performed by the Scientific Registry of Transplant Recipients (SRTR). All aspects of the analytical process are discussed, including cohort selection, post-transplant follow-up analysis, outcome definition, ascertainment of events, censoring, and adjustments. The methods employed for descriptive analyses are described, such as unadjusted mortality rates and survival probabilities, and the estimation of covariant effects through regression modeling. A section on transplant waiting time focuses on the kidney and liver waiting lists, pointing out the different considerations each list requires and the larger questions that such analyses raise. Additionally, this article describes specialized modeling strategies recently designed by the SRTR and aimed at specific organ allocation issues. The article concludes with a description of simulated allocation modeling (SAM), which has been developed by the SRTR for three organ systems: liver, thoracic organs, and kidney-pancreas. SAMs are particularly useful for comparing outcomes for proposed national allocation policies. The use of SAMs has already helped in the development and implementation of a new policy for liver candidates with high MELD scores to be offered organs regionally before the organs are offered to candidates with low MELD scores locally. [source] Long QT Syndrome in Patients over 40 Years of Age: Increased Risk for LQTS-Related Cardiac Events in Patients with Coronary DiseaseANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2008Edward Sze B.A. Background: Previous studies of long QT syndrome (LQTS) have focused primarily on the clinical course of affected patients up to 40 years of age to avoid the confounding influence of acquired heart disease on LQTS-related cardiac events in this genetic disorder. Methods: Patients were identified as having coronary disease if they had a history of hospitalization for myocardial infarction, coronary angioplasty, coronary artery bypass graft surgery, or were treated with medication for angina. LQTS-related cardiac events included the first occurrence of syncope, aborted cardiac arrest, or sudden cardiac death without evidence suggestive of an acute coronary event. Cox proportional hazards regression modeling was used to analyze the independent contribution of coronary disease to LQTS-related cardiac events. Results: Time-dependent coronary disease was associated with an increased risk of LQTS-related cardiac events (hazard ratio 2.24, 95% confidence interval 1.23,4.07, P = 0.008) after adjustment for syncopal history before age 40, QTc, and gender. Factors such as diabetes and hypertension that increase the risk for coronary disease were not associated with an increased risk for LQTS-related cardiac events. Conclusions: This is the first study to demonstrate that coronary disease augments the risk for LQTS-related cardiac events in LQTS. The findings highlight the need for more focused preventive therapy in LQTS patients above the age of 40. [source] Premature atherosclerosis in pediatric systemic lupus erythematosus: Risk factors for increased carotid intima-media thickness in the atherosclerosis prevention in pediatric lupus erythematosus cohort,ARTHRITIS & RHEUMATISM, Issue 5 2009Laura E. Schanberg Objective To evaluate risk factors for subclinical atherosclerosis in a population of patients with pediatric systemic lupus erythematosus (SLE). Methods In a prospective multicenter study, a cohort of 221 patients underwent baseline measurements of carotid intima-media thickness (CIMT) as part of the Atherosclerosis Prevention in Pediatric Lupus Erythematosus (APPLE) trial. SLE disease measures, medications, and traditional risk factors for atherosclerosis were assessed. A standardized protocol was used to assess the thickness of the bilateral common carotid arteries and the mean maximal IMT of 12 segments. Univariable analysis identified potential associations with CIMT, which were examined in multivariable linear regression modeling. Results Based on the mean-mean common or the mean-max CIMT as the dependent variable, univariable analysis showed significant associations of the following variables with increased CIMT: increasing age, longer SLE duration, minority status, higher body mass index (BMI), male sex, increased creatinine clearance, higher lipoprotein(a) level, proteinuria, azathioprine treatment, and prednisone dose. In multivariable modeling, both azathioprine use (P = 0.005 for the mean-mean model and P = 0.102 for the mean-max model) and male sex (P < 0.001) were associated with increases in the mean-max CIMT. A moderate dosage of prednisone (0.15,0.4 mg/kg/day) was associated with decreases in the mean-max CIMT (P = 0.024), while high-dose and low-dose prednisone were associated with increases in the mean-mean common CIMT (P = 0.021) and the mean-max CIMT (P = 0.064), respectively. BMI (P < 0.001) and creatinine clearance (P = 0.031) remained associated with increased mean-mean common CIMT, while increasing age (P < 0.001) and increasing lipoprotein(a) level (P = 0.005) were associated with increased mean-max CIMT. Conclusion Traditional as well as nontraditional risk factors were associated with increased CIMT in this cohort of patients in the APPLE trial. Azathioprine treatment was associated with increased CIMT. The relationship between CIMT and prednisone dose may not be linear. [source] Contribution of congestive heart failure and ischemic heart disease to excess mortality in rheumatoid arthritis,,ARTHRITIS & RHEUMATISM, Issue 1 2006Paulo J. Nicola Objective Although mortality among patients with rheumatoid arthritis (RA) is higher than in the general population, the relative contribution of comorbid diseases to this mortality difference is not known. This study was undertaken to evaluate the contribution of congestive heart failure (CHF) and ischemic heart disease (IHD), including myocardial infarction, to the excess mortality in patients with RA, compared with that in individuals without RA. Methods We assembled a population-based inception cohort of individuals living in Rochester, Minnesota, in whom RA (defined according to the criteria of the American College of Rheumatology [formerly, the American Rheumatism Association]) first developed between 1955 and 1995, and an age- and sex-matched non-RA cohort. All subjects were followed up until either death, migration from the county, or until 2001. Detailed information from the complete medical records was collected. Statistical analyses included the person-years method, cumulative incidence, and Cox regression modeling. Attributable risk analysis techniques were used to estimate the number of RA deaths that would be prevented if the incidence of CHF was the same in patients with RA and non-RA subjects. Results The study population included 603 patients with RA and 603 subjects without RA. During followup, there was an excess of 123 deaths among patients with RA (345 RA deaths occurred, although only 222 such deaths were expected). The mortality rates among patients with RA and non-RA subjects were 39.0 and 29.2 per 1,000 person-years, respectively. There was a significantly higher cumulative incidence of CHF (but not IHD) in patients with RA compared with non-RA subjects (37.1% versus 27.7% at 30 years of followup, respectively; P < 0.001). The risk of death associated with either CHF or IHD was not significantly different between patients with RA and non-RA subjects. If the risk of developing CHF was the same in patients with RA and individuals without RA, the overall mortality rate difference between RA and non-RA hypothetically would be reduced from 9.8 to 8.0 excess deaths per 1,000 person-years; that is, 16 (13%) of the 123 excess deaths could be prevented. Conclusion CHF, rather than IHD, appears to be an important contributor to the excess overall mortality among patients with RA. CHF contributes to this excess mortality primarily through the increased incidence of CHF in RA, rather than increased mortality associated with CHF in patients with RA compared with non-RA subjects. Eliminating the excess risk of CHF in patients with RA could significantly improve their survival. [source] Factors influencing medical oncology referral in Dukes' C colonic cancerASIA-PACIFIC JOURNAL OF CLINICAL ONCOLOGY, Issue 3 2010Cu-Tai LU Abstract Aim: Colorectal cancer (CRC) is one of the most common malignancies worldwide and adjuvant chemotherapy is proven to improve survival in patients with Dukes' C CRC. The purpose of this study was to analyze factors influencing referral to medical oncology in patients with Dukes' C colonic cancer in our institutions. Methods: Patients who underwent resection for Dukes' C colonic cancer were assessed for factors that influence the pattern of postoperative referral to the medical oncology department, including demographic and perioperative data. Results: Overall, 466 patients were identified to have Dukes' C colonic cancer, with 53.9% of these being female. Referral to medical oncology occurred for 58.4% patients. Multivariable logistic regression modeling identified age, elective admission and resection in private hospitals as factors. The likelihood of medical oncology referral in patients who had elective resection was 63% versus 41% in those who had emergency resection and resection in private hospitals was 69% versus 50% in public hospitals. Conclusion: Referral to a postoperative medical oncology clinic for adjuvant chemotherapy in Dukes' C colonic cancer was more likely in younger patients, those who underwent elective resection and those treated in private hospitals. [source] Association of natural fluoride in community water supplies with dental health of children in remote Indigenous communities , implications for policyAUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 3 2009Ross S. Bailie Abstract Objective: To map the geographic distribution of fluoride in water supplies and child dental caries in remote Indigenous communities of the Northern Territory (NT). To examine the association between fluoride levels, household and community factors, access to services and child dental caries in these communities and to model the impact on the caries experience of children of introducing water fluoridation. Methods: Fluoride testing was conducted in 80 locations across the NT in 2001. Measures of mean caries experience for six-year-olds and 12-year-olds and community and housing-related infrastructure were obtained from records of the NT School Dental Service. Associations between community fluoride levels, community level variables and childhood caries experience and potential impact of water fluoridation were assessed using linear regression modeling. Results: Mean caries experience for six- and 12-year-olds tended to be higher in northern and eastern areas of the NT, corresponding to the distribution of low levels of natural fluoride. Several-fold more children in remote NT communities are exposed to the risks of inadequate fluoride than are exposed to excessive fluoride. Mean reticulated fluoride level was the only variable significantly associated (p<0.05) with caries experience in both age groups. The potential reduction of caries through introducing water fluoridation is expected to be about 28% for children living in communities with the lowest levels of fluoride (<0.3 mg/L). Conclusions and Implications: Introduction of fluoridation of water supplies into communities with inadequate natural fluoride is a vital measure for improving the dental health of children living in remote NT communities. [source] Paramedic Self-efficacy and Skill Retention in Pediatric Airway ManagementACADEMIC EMERGENCY MEDICINE, Issue 12 2008Scott T. Youngquist MD Abstract Objectives:, The objectives were to determine the effect of pediatric airway management training on paramedic self-efficacy and skill performance and to determine which of several retraining methods is superior. Methods:, A total of 2,520 paramedics were trained to proficiency in pediatric bag-mask ventilation (BMV) and endotracheal intubation (ETI) on mannequins. Subjects were a convenience sample of 245 (10% of original cohort) presenting for voluntary retraining. A total of 212 of 245 (87%) completed skills testing. Self-efficacy was measured prior to and following initial training and retraining events. Paramedics were assigned to control (no retraining), videotape presentation, self-directed learning, or instructor-facilitated lecture and demonstration retraining. Following retraining, BMV and ETI skills were tested. Results:, Paramedics from low-call-volume areas reported lower baseline self-efficacy and derived larger increases with training, but also experienced the most decline between training events. Pass rates for BMV and ETI were 66% (139/211) and 42% (88/212), respectively. However, overall cohort self-efficacy was maintained over the study period. In ordinal regression modeling, only the lecture and demonstration method was superior to control, with an odds ratio (OR) of achieving higher scores of 2.5 (95% confidence interval [CI] = 1.2 to 5.2) for BMV and 5.2 (95% CI = 2.4 to 11.2) for ETI. Poor performance with ETI but not BMV was associated with time elapsed since training (p = 0.01). Self-efficacy ratings were not predictive of skill performance. Conclusions:, Training provides increases in self-efficacy, particularly among paramedics from low-call-volume areas. A gap exists between self-efficacy and skill performance, in that self-efficacy may be maintained even when skill performance declines. Pediatric airway skills decay quickly, ETI skills drop off more significantly than BMV skills, and a lecture and demonstration format seems superior to other retraining methods investigated. [source] | |||||||||||||||||||||||||||||||