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Multivariate Modeling (multivariate + modeling)
Selected AbstractsFunctional Impact of Relative Versus Absolute Sarcopenia in Healthy Older WomenJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 11 2007Marcos Estrada MD OBJECTIVES: To determine whether adjustment of muscle mass for height2 or for body mass represents a more-relevant predictor of physical performance. DESIGN: Cross-sectional study, using baseline data from a trial comparing upper- and lower-body training. SETTING: Women recruited from the community and gynecological practices in Connecticut. PARTICIPANTS: One hundred eighty-nine healthy older (aged 67.5 ± 4.8), active women receiving estrogen for osteoporosis over 2 years. MEASUREMENTS: Total and appendicular skeletal muscle (ASM) and fat mass (AFM) were determined using dual x-ray absorptiometry. Physical performance, muscle strength, and fitness measures were obtained at baseline. RESULTS: Adjusting ASM for height2 identifies lean women who are sarcopenic according to published standards yet fails to identify overweight and obese women whose ASM adjusted for body mass is low. ASM divided by body mass (ASM/body mass) is a stronger physical performance predictor, explaining 32.5%, 13.5%, 11.6%, 6.3%, and 6.8% of the variance in maximum time on treadmill, 6-minute walk, gait speed, 8-foot walk, and single leg stance, respectively, whereas ASM divided by height in m2 (ASM/height2) explained only 2.9%, 0.2%, 2.0%, 0.04%, and 0.1%. Multivariate modeling demonstrated considerable overlap in aspects of ASM/body mass and AFM/body mass associated with performance, with ASM/body mass dominant. In contrast, ASM/height2 is a much stronger predictor of leg press 1 repetition maximum and maximum power. CONCLUSION: The results suggest that relative sarcopenia with ASM adjusted for body mass is a better mobility predictor, with absolute sarcopenia a better indicator of isolated muscle group function in healthy postmenopausal women receiving estrogen replacement. [source] Analysis of video images from a gas,liquid transfer experiment: a comparison of PCA and PARAFAC for multivariate image analysisJOURNAL OF CHEMOMETRICS, Issue 7 2003Stephen P. Gurden Abstract The use of chemical imaging is a developing area which has potential benefits for chemical systems where spatial distribution is important. Examples include processes in which homogeneity is critical, such as polymerizations, pharmaceutical powder blending and surface catalysis, and dynamic processes such as the study of diffusion rates or the transport of environmental pollutants. Whilst single images can be used to determine chemical distribution patterns at a given point in time, dynamic processes can be studied using a sequence of images measured at regular time intervals, i.e. a movie. Multivariate modeling of image data can help to provide insight into the important chemical factors present. However, many issues of how best to apply these models remain unclear, especially when the data arrays involved have four or five different dimensions (height, width, wavelength, time, experiment number, etc.). In this paper we describe the analysis of video images recorded during an experiment to investigate the uptake of CO2 across a free air,water interface. The use of PCA and PARAFAC for the analysis of both single images and movies is described and some differences and similarities are highlighted. Some other image transformation techniques, such as chemical mapping and histograms, are found to be useful both for pretreatment of the raw data and for dimensionality reduction of the data arrays prior to further modeling. Copyright © 2003 John Wiley & Sons, Ltd. [source] Multivariate modeling of encapsulation and release of an ionizable drug from polymer microspheresJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2009Hagar I. Labouta Abstract In the formulation of polymer microspheres (MSs) loaded with verapamil hydrochloride (VRP), a low molecular weight ionizable drug, by W/O/W emulsification, the pH of the external aqueous phase proved to be a primary determinant of both IE and drug release behavior. Increasing the pH of the external aqueous phase enhanced IE (,100% at pH 8.4). This was associated with a considerable increase in initial release rate at pH 1.2. Two multivariate methods, factorial analysis (FA) and artificial neural network (ANN), were used to investigate the impact of the combined effect of the external phase pH and other parameters (polymer concentration and initial drug load) on MS characteristics; IE, initial drug release, MS size and yield. FA indicated that the external aqueous phase pH affected all responses, with a particularly strong correlation with IE in addition to a combined synergistic effect with polymer concentration on MS size. ANN showed better internal and external predictive ability of responses compared to FA. The ANN model developed in the study can be successfully used for multivariate modeling of the encapsulation and release of VRP and similar drug salts from hydrophobic polymer MSs prepared by multiple emulsification in addition to other MS characteristics. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4603,4615, 2009 [source] Carotid plaque computed tomography imaging in stroke and nonstroke patientsANNALS OF NEUROLOGY, Issue 2 2008Max Wintermark MD Objective To identify a set of computed tomographic (CT) features of carotid atherosclerotic plaques that is significantly associated with ischemic stroke. Methods In a cross-sectional study, we retrospectively identified 136 consecutive patients admitted to our emergency department with suspected stroke who underwent a CT-angiogram of the carotid arteries. CT-angiographic studies of the carotid arteries were processed automatically using automated computer classifier algorithm that quantitatively assesses a battery of carotid CT features. Acute stroke patients were categorized into "acute carotid stroke patients" and "nonacute carotid stroke patients" independent of carotid wall CT features, using the Causative Classification System for Ischemic Stroke, which includes the neuroradiologist's review of the imaging studies of the brain parenchyma and of the degree of carotid stenosis, and charted test results (such as electrocardiogram). Univariate followed by multivariate analyses were used to build models to differentiate between these patient groups and to differentiate between the infarct and unaffected sides in the "acute carotid stroke patients." Results Forty "acute carotid stroke" patients and 50 "nonacute carotid stroke" patients were identified. Multivariate modeling identified a small number of the carotid wall CT features that were significantly associated with acute carotid stroke, including wall volume, fibrous cap thickness, number and location of lipid clusters, and number of calcium clusters. Interpretation Patients with acute carotid stroke demonstrate significant differences in the appearance of their carotid wall ipsilateral to the side of their infarct, when compared with either nonacute carotid stroke patients or the carotid wall contralateral with the infarct side. Ann Neurol 2008;64:149,157 [source] The Proinflammatory Cytokine Response following Resuscitation in the Swine Model Depends on the Method of Ventricular Fibrillation InductionACADEMIC EMERGENCY MEDICINE, Issue 10 2008James T. Niemann MD Abstract Objectives:, A systemic inflammatory response has been reported following resuscitation from cardiac arrest. The purpose of this study was to compare the magnitude of the tumor necrosis factor-, (TNF-,) response in two different swine models of ventricular fibrillation (VF) arrest. Methods:, This was a randomized comparative trial conducted with domestic swine (N = 28, mean weight 40 kg, range 34,49 kg) of both genders. Anesthetized and instrumented swine were randomized to electrically induced VF (n = 14) or spontaneous VF induced by occlusion of a coronary artery (n = 14). After 8 minutes of VF, countershocks were given and standard advanced cardiac life support was initiated. Resuscitated animals were observed for 3 hours, and hemodynamics, base excess, and TNF-, concentrations were measured at intervals. Results:, TNF-, concentrations were significantly greater in the ischemic VF group throughout the postresuscitation period. Multivariate modeling demonstrated that the TNF-, level was dependent on the method of VF induction and correlated with ischemia time (untreated VF period plus time to restoration of circulation) and the degree of postresuscitation hypoperfusion as reflected in base excess measurements. Conclusions:, This study demonstrates that TNF-, concentrations increase after resuscitation from cardiac arrest and that the TNF-, response is more profound in animals subjected to ischemic, spontaneous VF. The observed differences may be due to a longer resuscitation time and persistent postresuscitation hypoperfusion in the ischemic VF group. These differences need to be considered in studies evaluating mechanisms of postresuscitation organ dysfunction and defining mortality markers. [source] Inappropriate Use of Antibiotics for Acute Asthma in United States Emergency DepartmentsACADEMIC EMERGENCY MEDICINE, Issue 8 2008Stefan G. Vanderweil BA Abstract Objectives:, The aim was to examine the use of antibiotics to treat asthma patients in U.S. emergency departments (EDs). The authors sought to investigate inappropriate antibiotic prescriptions by identifying the frequency and predictors of antibiotics prescribed for asthma exacerbations using data from two sources, the National Hospital Ambulatory Medical Care Survey (NHAMCS) and the National Emergency Department Safety Study (NEDSS). Methods:, The authors used data from NHAMCS and NEDSS to identify the proportion of ED visits for asthma exacerbations that resulted in the prescription of an antibiotic. NHAMCS provided national data from 1993 through 2004, while NEDSS provided data from 63 primarily academic EDs from 2003 through 2006. Univariate analysis and multivariate logistic regression modeling were used to identify variables associated with antibiotic administration. Results:, Analysis of NHAMCS data revealed that 22% (95% confidence interval [CI] = 20% to 24%) of acute asthma visits resulted in an antibiotic prescription from 1993 through 2004, with no significant change in prescribing frequency over the 12-year period. NEDSS data from 2003 through 2006 showed that 18% (95% CI = 17% to 19%) of acute asthma cases in academic EDs received an antibiotic. Multivariate modeling of NHAMCS data revealed that African American patients (odds ratio [OR] = 0.8; 95% CI = 0.6 to 0.97) and patients in urban EDs (OR = 0.5; 95% CI = 0.4 to 0.7) were less likely to receive antibiotics for asthma exacerbations than white patients and patients in nonurban EDs, respectively. NHAMCS analysis also found that patients in the South were more likely to receive antibiotics than those in the Northeast (OR = 1.4; 95% CI = 1.1 to 1.9). A NEDSS multivariate model found a similar difference, with African Americans (OR = 0.6; 95% CI = 0.4 to 0.8) and Hispanics (OR = 0.6; 95% CI = 0.4 to 0.8) being less likely than whites to receive an antibiotic. Conclusions:, ED treatment of acute asthma with unnecessary antibiotics is likely to contribute to bacterial antibiotic resistance. Interventions are needed to reduce inappropriate antibiotic prescriptions and to address disparities in asthma care. [source] Modeling the genetic and environmental association between peer group deviance and cannabis use in male twinsADDICTION, Issue 3 2009Nathan A. Gillespie ABSTRACT Background Peer group deviance (PGD) is linked strongly to liability to drug use, including cannabis. Our aim was to model the genetic and environmental association, including direction of causation, between PGD and cannabis use (CU). Method Results were based on 1736 to 1765 adult males from the Mid-Atlantic Twin Registry with complete CU and PGD data measured retrospectively at three time-intervals between 15 and 25 years using a life-history calendar. Results At all ages, multivariate modeling showed that familial aggregation in PGD was explained by a combination of additive genetic and shared environmental effects. Moreover, the significant PGD,CU association was best explained by a CU,PGD causal model in which large portions of the additive genetic (50,78%) and shared environmental variance (25,73%) in PGD were explained by CU. Conclusions Until recently PGD was assumed to be an environmental, upstream risk factor for CU. Our data are not consistent with this hypothesis. Rather, they suggest that the liability to affiliate with deviant peers is explained more clearly by a combination of genetic and environmental factors that are indexed by CU which sits as a ,risk indicator' in the causal pathway between genetic and environmental risks and the expression of PGD. This is consistent with a process of social selection by which the genetic and environmental risks in CU largely drive the propensity to affiliate with deviant peers. [source] Factors associated with treatment nonadherence among US bipolar disorder patients,HUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 2 2008Ross J. Baldessarini Abstract Objective Since sustained treatment-adherence is often problematic and may limit clinical outcomes among bipolar disorder (BPD) patients, we sought risk factors to guide clinical prediction of nonadherence. Methods Data were from a 2005 US national sample providing questionnaire responses by 131 randomly selected prescribing psychiatrists and their adult BPD patients. We contrasted demographic and clinical factors in treatment-adherent versus nonadherent patients (strictly defined as missing ,1 dose within 10 days) in univariate analyses followed by multivariate logistic-regression modeling. Results Of 429 DSM-IV BPD patients (79% type-I; 62% women; 17% minorities), 34% reported missing,,,1 dose of psychotropic medication within 10 days, 20% missed entire daily doses at least once, and only 2.5% missed all doses for 10 days. However, their prescribing psychiatrists considered only 6% as treatment-nonadherent. Factors significantly associated with nonadherence in multivariate modeling ranked: alcohol-dependence,>,youth,>,greater affective morbidity,>,various side effects,,,comorbid obsessive-compulsive disorder,,,recovering from mania-hypomania. Unrelated were sex, diagnostic subtype, and other comorbidities. Since most patients received,,,2 psychotropics, potential relationships between treatment-complexity and adherence were obscured. Conclusions Prevalent treatment-nonadherence among American BPD patients, and striking underestimation of the problem by prescribing clinicians may encourage increasingly complex treatment-regimens of untested value, but added expense, risk of adverse effects, and uncertain impact on treatment-adherence itself. Copyright © 2007 John Wiley & Sons, Ltd. [source] Multivariate modeling of encapsulation and release of an ionizable drug from polymer microspheresJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2009Hagar I. Labouta Abstract In the formulation of polymer microspheres (MSs) loaded with verapamil hydrochloride (VRP), a low molecular weight ionizable drug, by W/O/W emulsification, the pH of the external aqueous phase proved to be a primary determinant of both IE and drug release behavior. Increasing the pH of the external aqueous phase enhanced IE (,100% at pH 8.4). This was associated with a considerable increase in initial release rate at pH 1.2. Two multivariate methods, factorial analysis (FA) and artificial neural network (ANN), were used to investigate the impact of the combined effect of the external phase pH and other parameters (polymer concentration and initial drug load) on MS characteristics; IE, initial drug release, MS size and yield. FA indicated that the external aqueous phase pH affected all responses, with a particularly strong correlation with IE in addition to a combined synergistic effect with polymer concentration on MS size. ANN showed better internal and external predictive ability of responses compared to FA. The ANN model developed in the study can be successfully used for multivariate modeling of the encapsulation and release of VRP and similar drug salts from hydrophobic polymer MSs prepared by multiple emulsification in addition to other MS characteristics. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4603,4615, 2009 [source] Quality by design, part I: Application of NIR spectroscopy to monitor tablet manufacturing processJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2008Simin Hassannejad Tabasi Abstract To monitor tableting production using near infrared (NIR) spectroscopy, chemometric models were developed to analyze peak compression force, crushing strength and content uniformity. To measure tablet content uniformity, orbifloxacin tablets with drug content ranging from 60 to 90 mg were made and analyzed using ultraviolet (UV) and NIR spectroscopy. To assess the compression force and crushing strength, several batches of tablets were made on a Stokes B2 rotary tablet press and compression force was varied from 360 to 3500 lb. Principal component analysis (PCA) was used to identify tablets with regular and capped tablets breakage patterns. Comparison of statistical parameters showed that partial least squares (PLS) models gave better fit than the multiple linear regression (MLR) models. The best fit PLS models had a standard error of calibration (SEC) and a standard error of prediction (SEP) for content uniformity of 1.13 and 1.36 mg; for compression force of 69.86 and 59.48 lb and for crushing strength 0.55 kP and 0.57 kP, respectively. NIR spectroscopy in combination with multivariate modeling is a rapid and nondestructive technique that could reliably predict content uniformity, compression force and crushing strength for orbifloxacin tablets. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4040,4051, 2008 [source] Qualitative in situ analysis of multiple solid-state forms using spectroscopy and partial least squares discriminant modelingJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2007Karin Kogermann Abstract This study used in situ spectroscopy to reveal the multiple solid-state forms that appear during isothermal dehydration. Hydrate forms of piroxicam and carbamazepine (CBZ) were investigated on hot-stage at different temperatures using near-infrared (NIR) and Raman spectroscopy combined with multivariate modeling. Variable temperature X-ray powder diffraction, differential scanning calorimetry, thermogravimetric analysis, and Karl Fisher titrimetry were used as reference methods. Partial least squares discriminant analysis (PLS-DA) was performed to qualitatively evaluate the phase transition. It was shown that the constructed PLS-DA models, where spectral differences were directly correlated to solid-state modifications, enabled differentiation between the multiple forms. Qualitative analysis revealed that during dehydration, hydrates, such as CBZ dihydrate, may go through several solid-state forms, which must be considered in quantitative model construction. This study demonstrates that in situ analysis can be used to monitor the dehydration and reveal associated solid-state forms prior to quantification. The utility of the complementary spectroscopic techniques, NIR and Raman, have been shown. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1802,1820, 2007 [source] Assessing risk of violent behavior among veterans with severe mental illness,JOURNAL OF TRAUMATIC STRESS, Issue 1 2008Eric B. Elbogen Although empirical research has examined factors associated with increased violence risk among individuals with severe mental illness (SMI) and among veterans without SMI, less attention has been devoted to identifying violence risk factors among veterans with SMI. Using multivariable analysis of a large pooled sample of individuals with SMI, this study examines violence risk factors of N = 278 veterans with SMI. In multivariate modeling, violence by veterans with SMI was associated with head injury, posttraumatic stress disorder (PTSD), substance abuse, and homelessness. Results support the view clinicians assessing violence risk among veterans with SMI should consider a combination of characteristics empirically related to violence by non-veterans with SMI (e.g., homelessness) and veterans without SMI (e.g., PTSD). [source] | |||||||||||||