Search results for "Multivariable"
showing 9 items of 39 documents
Tailoring sparse multivariable regression techniques for prognostic single-nucleotide polymorphism signatures.
2011
When seeking prognostic information for patients, modern technologies provide a huge amount of genomic measurements as a starting point. For single-nucleotide polymorphisms (SNPs), there may be more than one million covariates that need to be simultaneously considered with respect to a clinical endpoint. Although the underlying biological problem cannot be solved on the basis of clinical cohorts of only modest size, some important SNPs might still be identified. Sparse multivariable regression techniques have recently become available for automatically identifying prognostic molecular signatures that comprise relatively few covariates and provide reasonable prediction performance. For illus…
Comparison between splines and fractional polynomials for multivariable model building with continuous covariates: a simulation study with continuous…
2012
In observational studies, many continuous or categorical covariates may be related to an outcome. Various spline-based procedures or the multivariable fractional polynomial (MFP) procedure can be used to identify important variables and functional forms for continuous covariates. This is the main aim of an explanatory model, as opposed to a model only for prediction. The type of analysis often guides the complexity of the final model. Spline-based procedures and MFP have tuning parameters for choosing the required complexity. To compare model selection approaches, we perform a simulation study in the linear regression context based on a data structure intended to reflect realistic biomedica…
On stability issues in deriving multivariable regression models
2014
In many areas of science where empirical data are analyzed, a task is often to identify important variables with influence on an outcome. Most often this is done by using a variable selection strategy in the context of a multivariable regression model. Using a study on ozone effects in children (n = 496, 24 covariates), we will discuss aspects relevant for deriving a suitable model. With an emphasis on model stability, we will explore and illustrate differences between predictive models and explanatory models, the key role of stopping criteria, and the value of bootstrap resampling (with and without replacement). Bootstrap resampling will be used to assess variable selection stability, to d…
What is Differential Stochastic Calculus?
1999
Some well known concepts of stochastic differential calculus of non linear systems corrupted by parametric normal white noise are here outlined. Ito and Stratonovich integrals concepts as well as Ito differential rule are discussed. Applications to the statistics of the response of some linear and non linear systems is also presented.
Birth weight, adult weight, and cardiovascular biomarkers : Evidence from the Cardiovascular Young Finns Study
2021
This study quantifies the causal effect of birth weight on cardiovascular biomarkers in adulthood using the Cardiovascular Risk in Young Finns Study (YFS). We apply a multivariable Mendelian randomization (MVMR) method that provides a novel approach to improve inference in causal analysis based on a mediation framework. The results show that birth weight is linked to triglyceride levels (β = −0.294; 95% CI [−0.591, 0.003]) but not to low-density lipoprotein (LDL) cholesterol levels (β = 0.007; 95% CI [−0.168, 0.183]). The total effect of birth weight on triglyceride levels is partly offset by a mediation pathway linking birth weight to adult BMI (β = 0.111; 95% CI [−0.013, 0.234]). The nega…
El papel de la reputación del Consejero Delegado en la reputación de la empresa española
2010
La reputación corporativa se conceptúa como la estimación global de las percepciones que tienen de la empresa sus principales stakeholders. La literatura ha visto en la reputación corporativa uno de los activos intangibles más valioso desde el punto de vista de la creación y sostenimiento de ventajas competitivas, por lo que diversos estudios han tratado de identificiar los antecedentes de la reputación de la empresa. Uno de estos antecedentes destacado son sus directivos, y entre ellos los Consejeros Delegados. En España, los trabajos sobre los antecedentes de la reputación corporativa son muy escasos, e inexistentes los que han abordado el estudio de la influencia de la reputación del Con…
The association of patient age with postoperative morbidity and mortality following resection of intracranial tumors
2021
Abstract Introduction The postoperative functional status of patients with intracranial tumors is influenced by patient-specific factors, including age. Research question This study aimed to elucidate the association between age and postoperative morbidity or mortality following the resection of brain tumors. Material and methods A multicenter database was retrospectively reviewed. Functional status was assessed before and 3–6 months after tumor resection by the Karnofsky Performance Scale (KPS). Uni- and multivariable linear regression were used to estimate the association of age with postoperative change in KPS. Logistic regression models for a ≥10-point decline in KPS or mortality were b…
Does Oxygen Content Play a Role in Spontaneous Closure of Perimembranous Ventricular Septal Defects?
2021
(1) Background: the impact of a series of laboratory parameters (haemoglobin, haematocrit, foetal haemoglobin, peripheral oxygen saturation, iron, transferrin, ferritin, and albumin) on perimembranous ventricular septal defects spontaneous healing was tested. (2) Methods: one hundred and seven patients were enrolled in the study (57% males; mean age 2.1 ± 0.4 years) and were subsequently subdivided into two groups: self-healing (n = 36) and in need of intervention (n = 71). Self-healing subjects were defined on the basis of an absence of residual shunts at colorDoppler across the previous defect. (3) Results: no statistically significant differences were reported in the size of perimembrano…
Detección de nuevos marcadores asociados a daño por reperfusión y fibrosis en infarto de miocardio validados histopatológicamente mediante análisis m…
2022
La resonancia magnética cardiovascular (RMC) con realce tardío es la técnica de referencia para la evaluación no invasiva del daño cardíaco después de un infarto de miocardio (IM). Sin embargo, la interpretación de estas imágenes en términos de daño tisular es aún complicado y el uso de agentes de contraste en esta técnica está contraindicado en un amplio sector de la población con insuficiencia renal crónica. La microscopía de resonancia magnética (MRM) proporciona un nivel de detalle comparable al objetivo macroscópico de la microscopía óptica. Por ello, podría ser una herramienta muy útil en la interpretación de la imagen de RMC y en la identificación de nuevos marcadores de imagen de re…