Search results for "regression"
showing 10 items of 2619 documents
Reproducing kernel hilbert spaces regression methods for genomic assisted prediction of quantitative traits.
2008
Abstract Reproducing kernel Hilbert spaces regression procedures for prediction of total genetic value for quantitative traits, which make use of phenotypic and genomic data simultaneously, are discussed from a theoretical perspective. It is argued that a nonparametric treatment may be needed for capturing the multiple and complex interactions potentially arising in whole-genome models, i.e., those based on thousands of single-nucleotide polymorphism (SNP) markers. After a review of reproducing kernel Hilbert spaces regression, it is shown that the statistical specification admits a standard mixed-effects linear model representation, with smoothing parameters treated as variance components.…
Assessment of Granger causality by nonlinear model identification: application to short-term cardiovascular variability.
2007
A method for assessing Granger causal relationships in bivariate time series, based on nonlinear autoregressive (NAR) and nonlinear autoregressive exogenous (NARX) models is presented. The method evaluates bilateral interactions between two time series by quantifying the predictability improvement (PI) of the output time series when the dynamics associated with the input time series are included, i.e., moving from NAR to NARX prediction. The NARX model identification was performed by the optimal parameter search (OPS) algorithm, and its results were compared to the least-squares method to determine the most appropriate method to be used for experimental data. The statistical significance of…
Mutual nonlinear prediction of cardiovascular variability series: Comparison between exogenous and autoregressive exogenous models
2007
A model-based approach to perform mutual nonlinear prediction of short cardiovascular variability series is presented. The approach is based on identifying exogenous (X) and autoregressive exogenous (ARX) models by K-nearest neighbors local linear approximation, and estimates the predictability of a series given the other as the squared correlation between original and predicted values of the series. The method was first tested on simulations reproducing different types of interaction between non-identical Henon maps, and then applied to heart rate (HR) and blood pressure (BP) variability series measured in healthy subjects at rest and after head-up tilt. Simulations showed that different c…
Procedimento estratégico em três estágios de seleção de variáveis para a obtenção de resultados equilibrados na pesquisa em saúde pública
2018
Multidisciplinary research in public health is approached using methods from many scientific disciplines. One of the main characteristics of this type of research is dealing with large data sets. Classic statistical variable selection methods, known as “screen and clean”, and used in a single-step, select the variables with greater explanatory weight in the model. These methods, commonly used in public health research, may induce masking and multicollinearity, excluding relevant variables for the experts in each discipline and skewing the result. Some specific techniques are used to solve this problem, such as penalized regressions and Bayesian statistics, they offer more balanced results a…
Evaluating the effect of organization and context on technical efficiency: a second-stage DEA analysis of Italian hospitals
2022
Objective: the purpose of this study was to compare the technical efficiency of Italian hospitals at a regional level and to examine if differences could be explained by organisational and contextual factors. Technical efficiency was defined as the ability of the operating units evaluated to use optimal resource levels for their level of output.Methods: the effect of external factors was explored through a second stage Data Envelopment Analysis (DEA). Efficiency scores were calculated for each hospital using the DEA method (Stage I). Through Tobit regression analysis, the estimated efficiency scores were regressed against a set of organisational and contextual characteristics beyond manager…
HELMINTH ASSEMBLAGES OF WHITEFISH (COREGONUS LAVARETUS) IN INTERCONNECTED LAKES: SIMILARITY AS A FUNCTION OF SPECIES SPECIFIC PARASITES AND GEOGRAPHI…
2004
This article examined the composition of parasite assemblages of whitefish (Coregonus lavaretus) in 8 interconnected lakes in northeastern Finland and evaluated the role of coregonid specific parasites and the geographical distance between populations in determining the similarity of the assemblages. Parasite assemblages were compared using the Jaccard qualitative similarity index and a quantitative similarity index and by incorporating the allogenic-autogenic species concept and the effects of 2 corresponding measures of geographical distance between the lakes. The majority of the parasite species found (10 of 14) were specific to salmonids. Similarity of assemblages of autogenic parasites…
Predictors of residual T1 high grade on re-transurethral resection in a large multi-institutional cohort of patients with primary T1 high-grade/grade…
2018
The aim of this multi-institutional study was to identify predictors of residual high-grade (HG) disease at re-transurethral resection (reTUR) in a large cohort of primary T1 HG/Grade 3 (G3) bladder cancer patients. A total of 1155 patients with primary T1 HG/G3 bladder cancer from 13 academic institutions that underwent a reTUR within 6 weeks after first TUR were evaluated. Logistic regression analysis was performed to assess the association of predictive factors with residual HG at reTUR. Residual HG cancer was found in 288 (24.9%) of patients at reTUR. Patients presenting residual HG cancer were more likely to have carcinoma in situ (CIS) at first resection (p=25 kg/m2. On multivariable …
Modified locally weighted—Partial least squares regression improving clinical predictions from infrared spectra of human serum samples
2012
Locally weighted partial least squares regression (LW-PLSR) has been applied to the determination of four clinical parameters in human serum samples (total protein, triglyceride, glucose and urea contents) by Fourier transform infrared (FTIR) spectroscopy. Classical LW-PLSR models were constructed using different spectral regions. For the selection of parameters by LW-PLSR modeling, a multi-parametric study was carried out employing the minimum root-mean square error of cross validation (RMSCV) as objective function. In order to overcome the effect of strong matrix interferences on the predictive accuracy of LW-PLSR models, this work focuses on sample selection. Accordingly, a novel strateg…
Glycated albumin as a glycaemic marker in patients with advanced chronic kidney disease and anaemia: a preliminary report.
2019
BACKGROUND: The association between glycated albumin (GA) and glycaemic status has not been fully described in patients with advanced chronic kidney disease (CKD) in relation to anaemia. The aim of this study was to evaluate the relationship between GA and fasting plasma glucose (FPG) and HbA1c in patients with advanced CKD and to evaluate the influence of anaemia in such relationship. MATERIALS AND METHODS: Patients with CKD stage 4 or 5 were included in the study. eGFR was calculated by the CKD-EPI creatinine equation. Plasma GA was measured by an enzymatic method. RESULTS: Eighty-one patients were included in the study, 46 (57%) were males; the mean age was 67 ± 14 years. HbA1c was corre…
Hepatic steatosis and insulin resistance are associated with severe fibrosis in patients with chronic hepatitis caused by HBV or HCV infection.
2011
BACKGROUND AND AIMS: Steatosis and insulin resistance (IR) are the major disease modifying in patients with chronic hepatitis C (CHC). Only few studies evaluated these features in patients with chronic hepatitis B (CHB). We aimed to assess the prevalence and the factors related to steatosis and IR in CHB patients, compared with CHC subjects, and to evaluate the potential association between these features and fibrosis severity. MATERIAL AND METHODS: One hundred and seventy consecutive patients with CHB (28 HBeAg positive, 142 HBeAg negative), were evaluated using liver biopsy and metabolic measurements and matched for sex, age and body mass index with 170 genotype 1 CHC patients. IR was def…