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At least 127 records · Page 7Linked to original sources

PubMed1978

Regression analysis in interlaboratory surveys: a case study with cholesterol and triglycerides.

1. A new interlaboratory survey design, that uses regression analysis to compare results from each laboratory with target values, was tested using cholesterol and triglyceride analyses. The fifty New Zealand laboratories involved showed considerable interlaboratory variation (CV = 8% to 27% for cholesterol, 13% to 113% for triglycerides), 30% and 40% of which was associated with systematic differences between laboratories. 2. End-of-period summaries using regression analysis confirmed the presence of systematic errors. These were either simple types caused apparently by incorrect standardisation (regression slope, B not equal to 1.0) or inappropriate blank correction (intercept, A not equal to zero) or complex types presumably due to nonlinearity or nonspecificity. Graphical display of results from each laboratory aided fault diagnosis and allowed the detection of between-run standardisation differences. 3. Method comparison studies were made: the only highly significant result being lower precision achieved by enzymatic cholesterol methods compared with other colorimetric methods.

Blood Chemical Analysis↗

PubMed1999

[Logistic regression analysis of female drug abusers' social-psychological factors].

OBJECTIVE: To study the social-psychological health status on female drug abusers. METHODS: Case-control study and logistic regression analysis. RESULTS: Results of simple logistic regression showed that factors with significant ORs were low education level, unemployment, marital status, senseless of life, self-killing, horror, madness, depression, insomnia, dizziness, perspiration, evil dream, divorce, setbacks of emotion, smoking, alcohol-abuse, playing truant, runaway from home, fighting, etc. The results of stepwise logistic regression analysis showed that factors entered the regression model were smoking, runaway from home, divorce, setbacks of emotion, marital status, hopeless toward life, level of education, dizziness, etc. CONCLUSION: Most female drug abusers' social-psychological status was poorer than controls preceding to their drug abuse, which contributed to the major causes of abuse drugs.

Adolescent↗

PubMed1994

[Comparative analysis of certain nutritional parameters of fat in food rations of various population groups. III. Use of correlation and regression analysis for assessment of the nutritional quality of fat].

Correlation and regression analysis demonstrated a high degree of correlation between saturated and monounsaturated fats, on the one hand, and the absolute fat content, and lower correlation with polyunsaturated fats. The increase of fat content raised the saturated fat content in the daily food rations of mental and physical workers with the lowest rise of polyunsaturated fatty acids. The rise of the per cent share of saturated fatty acids was always at the expense of monosaturated fatty acids whose content decreased. A similar change was observed in polyunsaturated fatty acids. From the standpoint of nutrition another unfavourable finding was the demonstrated negative correlation between monosaturated and polyunsaturated fatty acids.

Adult↗

PubMed2001

Validity of multiple-time regression analysis in measurement of tritiated and iodinated leptin crossing the blood-brain barrier: meaningful controls.

Multiple-time regression analysis has been used to study the influx of radiolabeled peptides and polypeptides across the blood-brain barrier (BBB). This study used both tritiated and iodinated leptin to clarify several issues associated with these measurements. Recombinant murine leptin was radiolabeled with 3H by derivatization or with 125I by the iodobead method and each studied separately in mice. Intact 3H-leptin had a higher apparent influx rate from blood to brain than did intact 125I-leptin, correlating with its higher proportion of reversible association with the capillary lumen that would misleadingly appear to reflect entry. Yet the majority of 3H-leptin and 125I-leptin reached brain parenchyma. There was no significant difference in the influx rate between cerebral cortex and the subcortical regions, thus ruling out a predominant contribution of simple diffusion through the circumventricular organs or choroid plexuses outside the BBB. The influx of radiolabeled leptin, especially 125I-leptin, was decreased by excess unlabeled leptin, supporting the presence of a saturable transport system for leptin at the BBB. To identify the specificity of the transport system and determine whether it is shared by 3H-leptin and 125I-leptin, these radioactively labeled leptins were heat-denatured. Denaturation had no effect on the fast influx of 3H-leptin, but abolished the entry of 125I-leptin into brain; excess denatured leptin failed to inhibit the influx of either 3H-leptin or 125I-leptin. This indicates that the conformation of 125I-leptin is similar to that of native unlabeled leptin, so that iodination would be the better choice for investigating the interaction of leptin with the BBB. However, 3H-leptin can use the same transport system, as shown by inhibition of its influx by unlabeled leptin, whereas the derivatization procedure altered its biophysical properties such that its non-saturated influx was greatly enhanced. Finally, the rapid influx of radioactively labeled leptin contrasted greatly with that of the reference compounds 99mTc-albumin and 3H-inulin which had no significant penetration of the BBB. Thus, with additional considerations such as stability and interactions with the vasculature, multiple-time regression analysis is sensitive and selective for study of the penetration of peptides across the BBB.

Animals↗

PubMed2001

A semi-parametric regression analysis of CD4 cell counts.

This paper considers the regression analysis of CD4 cell counts, a commonly used indicator and prognostic factor of AIDS progression. For this purpose, a number of methods have been proposed and most of them are based on random effects models. We present an alternative that is based on a mean function regression model. The new method is more natural and particularly appropriate if population parameters such as treatment comparison are mainly of interest. To estimate regression parameters, we present an estimating equation-based approach, which does not require estimation of the baseline mean function. This makes the implementation of the approach and the study of the properties of the estimated regression parameters much easier than those based on random effects models. The method is illustrated with a set of CD4 cell count data arising from an AIDS clinical trial and simulated data.

Acquired Immunodeficiency Syndrome↗

PubMed1984

Multiple regression analysis. Evaluation of low back pain syndrome (preliminary report).

In the objective judgment of the therapeutic effects and in the comparison of results in institutions and treatment methods, it is essential to introduce the technique of scientific and statistical analysis, in the clinical evaluation. We have tried to clinically evaluate lumbago and sciatica using the technique of multiple regression analysis. Selection of evaluation item and allocation of scores to the item were carried out in 104 patients. Multiple regression analysis was carried out in all patients and the standard regression coefficient showed a correlation with criterion variable (dependent Y) in the order of walking, pain, posture, paralytic symptom in lower limbs and SLR (straight leg raising test). The proportion was 0.69, which seems to be a nearly valid value when other factors are considered.

Back Pain↗

PubMed2003

Prediction of human pharmacokinetics from animal data and molecular structural parameters using multivariate regression analysis: oral clearance.

The aim of the study reported here was to develop a regression equation for predicting oral clearance of various kinds of drugs in humans using experimental data from rats and dogs and molecular structural parameters. The data concerning the oral clearance of 87 drugs from rats, dogs, and humans were obtained from literature. The compounds have various structures, pharmacological activities, and pharmacokinetic characteristics. In addition, the molecular weight, calculated partition coefficient (c log P), and the number of hydrogen bond acceptors were used as possible descriptors related to oral clearance in human. Multivariate regression analyses, multiple linear regression analysis, and the partial least squares (PLS) method were used to predict oral clearance in human, and the predictive performances of these techniques were compared by allometric approaches, which have been used in interspecies scaling. Interaction terms were also introduced into the regression analysis to evaluate the nonlinear relationship. For the data set used in this study, the PLS model with the tertiary term descriptors gave the best predictive performance, and the value of the squared cross-validated correlation coefficient (q(2)) was 0.694. This PLS model, using animal oral clearance data for only two species and easily calculated molecular structural parameters, can generally predict oral clearance in human better than the allometric approaches. In addition, the molecular structural parameters and the interaction term descriptors were useful for predicting oral clearance in human by PLS. Another advantage of this PLS model is that it can be applied to drugs with various characteristics.

Administration, Oral↗

PubMed1980

Multiple regression analysis on factors associated with nasal carriage of antibiotic-resistant Staphylococcus aureus and it's representation as a graphical model.

The results of a multiple regression analysis on the nasal carriage of antibiotic-resistant Staphylococcus aureus and the four major patient parameters, age, length of stay in hospital, sex and antibiotic use, is reported. The multiple correlation coefficient of the regression analysis was high and all the regression coefficients of the independent variables were statistically significant, confirming the validity of the analysis. Further, an analysis on the four patient parameters confirmed that the parameters are not correlated, hence the possibility of a bias being introduced into the regression model through interactions between the parameters is excluded. The resulting regression model was then studied and an application given with respect to an infection.

Adolescent↗

PubMed1984

Ecologic regression analysis and the study of the influence of air quality on mortality.

This presentation focuses entirely on the use and evaluation of regression analysis applied to ecologic data as a method to study the effects of ambient air pollution on mortality rates. Using extensive national data on mortality, air quality and socio-economic status regression analyses are used to study the influence of air quality on mortality. The analytic methods and data are selected in such a way that direct comparisons can be made with other ecologic regression studies of mortality and air quality. Analyses are performed by use of two types of geographic areas, age-specific mortality of both males and females and three pollutants (total suspended particulates, sulfur dioxide and nitrogen dioxide). The overall results indicate no persuasive evidence exists of a link between air quality and general mortality levels. Additionally, a lack of consistency between the present results and previous published work is noted. Overall, it is concluded that linear regression analysis applied to nationally collected ecologic data cannot be used to usefully infer a causal relationship between air quality and mortality which is in direct contradiction to other major published studies.

Air Pollutants↗

PubMed1994

Multiple regression analysis suggests motifs for class II MHC binding.

Multiple regression analysis is utilized to predict peptides that bind major histocompatibility complex (MHC) class II molecules of the d haplotype. The predictor variables, obtained from the primary sequence of protein fragments, include pairs of amino acid residues separated by zero to seven intervening residues. The resulting models demonstrate strong predictive validity, and have interpretations in accordance with recent discoveries regarding the binding mechanisms of class I MHC molecules.

Amino Acid Sequence↗

PubMed1998

A general approach for the prediction of the intestinal absorption of drugs: regression analysis using the physicochemical properties and drug-membrane electrostatic interaction.

A general method for predicting the intestinal absorption of a wide range of drugs using multiple regression analysis of their physicochemical properties and the drug-membrane electrostatic interaction was developed. The absorption rates of tested drugs from rat jejunum were measured by the in situ single-pass perfusion technique. The drugs used in this study were divided into three groups for regression analysis, and a smaller "test" set of compounds was used to assess the predictive capacity of the regression equation. When the analysis was applied to each respective group of drugs (i.e., anionic, cationic, and nonionized compounds), obtained regression coefficients were 0.569, 0.821, 0.728 by using the organic solvent (n-octanol)/buffer partition coefficient, 0.730, 0.734, 0.914 using the permeation rate across a silicon membrane, and 0.790, 0.915, 0.941 using an EVA membrane, respectively. However, smaller regression coefficients of 0.377, 0. 468, and 0.718 were obtained when these three groups of drugs were put together for prediction. Meanwhile, correlation was improved remarkably when drug-membrane electrostatic interactions, namely, hydrogen-bonding donor (Halpha) and acceptor (Hbeta) activity or index of electricity (Ec), were added to the other parameters of lipophilicity and permeation rate across the EVA membrane (r = 0.880 and 0.883, respectively). Moreover, the equation obtained from these regression analyses was applicable even to the prediction of the absorption of the zwitterionic drugs. These results suggest that including the electrostatic interaction parameters in addition to lipophilicity and permeability across artificial membranes would afford a better prediction for the intestinal absorption of the vast majority of drugs.

Animals↗

PubMed1988

Regression analysis in biological research: sample size and statistical power.

Regression analysis is often used to demonstrate associations among variables believed to be biologically related. Failure to demonstrate a "significant" relationship may be due to two factors: 1) the variables are truly unrelated, or 2) a relationship exists but goes undetected due to inadequate statistical power. Investigators must consider the second possibility since failure to detect a statistically significant relationship is often taken as evidence for no biological relationship. These issues are addressed in the context of the interrelationship between four features common to all statistical methods: the size of effect or relationship worth detecting, the Type I (alpha) error, the sample size, and the Type II (beta) error. An example derived from published data relating morphological characteristics of muscle fiber type and isokinetic strength performance illustrates the practical significance of this dilemma.

Regression Analysis↗

PubMed2006

Predicting iatrogenic gall bladder perforation during laparoscopic cholecystectomy: a multivariate logistic regression analysis of risk factors.

BACKGROUND: Seventeen independent risk factors were examined using multivariate logistic regression analysis to develop a profile of patients most likely at risk from iatrogenic gall bladder perforation (IGBP) during laparoscopic cholecystectomy. METHODS: Since 1989, a prospectively maintained database on 856 (women, 659; men, 197) consecutive laparoscopic cholecystectomies by a single surgeon (R. J. F.) was analysed. The mean age was 48 years (range, 17-94 years). The mean operating time was 88 min (range, 25-375 min) and the mean postoperative stay was 1 day (range, 1-24 days). There were 311 (women, 214; men, 97) IGBP. Seventeen independent variables, which included sex, race, history of biliary colic, dyspepsia, history of acute cholecystitis, acute pancreatitis and jaundice, previous abdominal surgery, previous upper abdominal surgery, medical illness, use of intraoperative laser or electrodiathermy, performance of intraoperative cholangiogram, positive intraoperative cholangiogram, intraoperative common bile duct exploration, presence of a grossly inflamed gall bladder as seen by the surgeon intraoperatively and success of the operation, were analysed using multivariate logistic regression for predicting IGBP. RESULTS: Multivariate logistic regression analysis against all 17 predictors was significant (chi(2) = 94.5, d.f. = 17, P = 0.0001), and the variables male sex, history of acute cholecystitis, use of laser and presence of a grossly inflamed gall bladder as seen by the surgeon intraoperatively were individually significant (P < 0.05) by the Wald chi(2)-test. CONCLUSION: Laparoscopic cholecystectomy, using laser, in a male patient with a history of acute cholecystitis or during an acute attack of cholecystitis is associated with a significantly higher incidence of IGBP.

Adolescent↗

PubMed2003

Pain dynamics observed by functional magnetic resonance imaging: differential regression analysis technique.

PURPOSE: To observe the dynamic responses of the cortical areas related to the pain processing by using the differential regression analysis (DRA) technique in functional magnetic resonance imaging (fMRI) and investigation of pain mechanisms. MATERIALS AND METHODS: For pain studies, thermal stimulation was applied by immersing the index finger into a hot bath of water with a temperature of 50-52 degrees C. Motor (finger tapping) and visual (flickering light) stimulation experiments were conducted to elucidate the physiological differences between the simple sensory tasks and pain tasks. To obtain dynamic responses, T values (regression analysis) were sequentially estimated by using a series of shifted differential window functions (narrow width). RESULTS: By using the DRA technique, well-defined prompt responses were observed for both motor and visual stimuli. On the other hand, in the pain experiment, a set of sequentially varying responses was observed for the thalamus (Thal), the dorsal anterior cingulate cortex (dACC), the caudal ACC (cACC), and the rostral ACC (rACC). This time-dependent response suggests the dynamics of pain signal processing in cortical areas. CONCLUSION: The results support the hypothesis that the activated areas are similar to the previously reported pain processing areas; however, new sequential responses were observed, suggesting that the technique may reveal dynamics of pain perception and their pathway, important elements in understanding the mechanism of pain. The DRA technique can provide a new opportunity for many spatiotemporal analyses, for example, the physiologically complex and little-studied physiological phenomena, such as pain dynamics.

Cerebral Cortex↗

PubMed1978

Estimation of age from the pubic symphysis by means of multiple regression analysis.

This study has been carried out to assess the age from the pubic symphysial surface employing a multiple regression analysis and a quantification theory model I analysis. Using partial regression coefficients and/or normalized scores obtained from the analyses, ages of skeletal remains can be quantitatively estimated with a fairly high reliability. The use of this method is, however, limited to the samples between 18 and 38 years of age, because age changes in the symphysial surface show large variations after about 40 years. The reliability of this method was also examined.

Adolescent↗

PubMed1992

Regression analysis of dexterity tests and dental students' practical examination results.

The desirability of some means of assessing potential dental students' dexterity is discussed and three new practical tests are described. Regression analysis was performed on the results and the subsequent correlations are presented. Further regression analysis was performed on examiners' scores in dental technology showing the inconsistencies. Results were not conclusive and it seems that the tests could possibly be used in an advisory role but little more.

Aptitude Tests↗

PubMed2003

Separation of individual-level and cluster-level covariate effects in regression analysis of correlated data.

The focus of this paper is regression analysis of clustered data. Although the presence of intracluster correlation (the tendency for items within a cluster to respond alike) is typically viewed as an obstacle to good inference, the complex structure of clustered data offers significant analytic advantages over independent data. One key advantage is the ability to separate effects at the individual (or item-specific) level and the group (or cluster-specific) level. We review different approaches for the separation of individual-level and cluster-level effects on response, their appropriate interpretation and give recommendations for model fitting based on the intent of the data analyst. Unlike many earlier papers on this topic, we place particular emphasis on the interpretation of the cluster-level covariate effect. The main ideas of the paper are highlighted in an analysis of the relationship between birth weight and IQ using sibling data from a large birth cohort study.

Birth Weight↗

PubMed1990

Application of regression analysis in the evaluation of tumor response following the administration of adriamycin either as a solution or via albumin microspheres to the rat.

Regression analysis has been applied to compare the tumor response following the administration of free and microsphere-loaded adriamycin to the rats. A nonmetastasizing sarcoma was induced in male A.S. inbred rats. When the sarcoma was in its fourth passage and 12 days old, four groups of animals received intratumoral injections of 2 or 8 mg/kg of adriamycin as a solution or via albumin microspheres. The animals in each group were monitored over a period of three weeks for changes in body weight and tumor size and their survival, and the results were statistically compared with the data obtained from an untreated group of animals (control). The use of regression analysis in conjunction with partial F-test revealed that the microsphere-delivered drug exhibited a meager but significantly greater response than the free drug. The implications of intratumoral administration of microsphere-loaded drug in the treatment of sarcomas is discussed.

Albumins↗