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Results for “Regression Analysis”

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At least 379 records · Page 21Linked to original sources

PubMed2005

Regression analysis between heart rate variability and baroreflex-related vagus nerve activity in rats.

INTRODUCTION: Many previous studies have suggested that the high-frequency (HF) power of the heart rate variability may represent cardiac vagal activity although direct evidence of a correlation between the HF and vagal neuronal activity is still lacking. In the present study, we performed a regression analysis of the HF and vagal neurograms. METHODS AND RESULTS: Experiments were carried out on adult male Sprague-Dawley rats anesthetized with a continuous infusion of pentobarbital sodium. The baroreflex-related vagus neuronal activities were obtained by nerve or single-fiber recordings. The transient baroreflex response was employed to alter vagus neuronal activities using a bolus injection of phenylephrine (PE). On-line power spectral analysis of the heart rate and a vagal neurogram was performed during the acute baroreflex response. During the test period, systemic arterial pressure immediately increased in response to the PE injection, after which the R-R interval (RR), HF (0.6-2.4 Hz), and vagus nerve and unit activities all dramatically increased. Both nerve and unit activities exhibited good correlations (r > or = 0.7 in all nerve recordings and r > or = 0.6 in 91% of single-fiber recordings) with the HF. There were insignificant differences between the right- and left-side baroreflex-related vagus nerve recordings. CONCLUSION: Our present study provides a direct linkage between the HF and vagus neuronal electrical activity in anesthetized rats.

Animals↗

PubMed1977

Factors influencing blood concentrations of chlordiazepoxide: a use of multiple regression analysis.

Three groups of male and female subjects aged 24-74 years received 25, 100, or 200 mg of chlordiazepoxide hydrochloride by mouth as a single dose or as two divided doses. The relation of plasma or whole blood concentrations for chlordiazepoxide (CDX) and its metabolite, desmethylchlordiazepoxide (DMCDX), to time since the last dose, weight, age, and sex were determined by simple and multiple regression analyses. Both CDX and DMCDX levels were negatively correlated with weight. Concentrations of CDX decreased, while those of DMCDX increased, with the time since the last dose. Lower levels of both drugs were associated with female sex, and lower levels of DMCDX were noted with increasing age. In the largest sample group, age and weight were more important variables than sex in accounting for CDX and DMCDX. Sex was of significance, and more important than time or age in explaining the variance of CDX in one series of observations. Multiple regression analysis is a useful approach to assessing interrelated factors influencing blood levels of drugs, especially when combined with a consideration of the interactive components of variance. Age and sex, in addition to weight and time, may be important factors that deserve further attention.

Adult↗

PubMed1981

Monitoring infectious diseases using routine microbiology data. II. An example of regression analysis used to study infectious gastroenteritis.

Routine data used to study infectious diseases may contain biases which obscure trends. A 16-year series (up to 1968) of routine laboratory data was used to study patterns of incidence of infective gastroenteritis for which no laboratory diagnosis could be made. An artificial pattern was detected. This arose because GPs tended to refer a greater proportion of their patients during dysentery epidemics. Multiple regression analysis was used to separate out this effect so that the underlying trends could be observed. The seasonal pattern of undiagnosed cases showed an autumn peak. There were also early-winter epidemics of disease with little or no excretion of red blood or pus cells in the diagnostic faeces specimen. Some of the winter communicable disease among older children and adults appeared to be associated with signs of a temporary fat malabsorption in pre-school age cases. Undiagnosed cases in older children and adults were not related to the E. coli serotypes causing disease in infants during this period. The statistical method applied increased the usefulness of these routine data. Although this series of laboratory records is now more than a decade old the results of the analysis can be compared with new observations as more is learned about the epidemiology of previously unrecognized pathogens, especially rotaviruses.

Adolescent↗

PubMed1999

Logistic regression analysis of small round cell neoplasms: a cytologic study.

The diagnosis of small round cell neoplasms (SRCN) in children is difficult by both histologic and cytologic methods. These neoplasms are unified morphologically by the scanty cytoplasm surrounding relatively round nuclei containing a primitive chromatin pattern. Further categorization is achieved histologically by the recognition of architectural differentiation and cytoplasmic features. Numerous series and case reports documenting the cytologic features of SRCN have been published in the English-language literature, but relatively few studies have statistically analyzed the diagnostic utility of these features. Our logistic regression analysis of 59 cases of SRCN indicates that the presence of an extremely scanty cytoplasm favors the diagnosis of Ewing's sarcoma (P = 0.004), as does the positive expression of cytoplasmic vacuoles (P = 0.02). Strap or tadpole cells closely correlate with the diagnosis of rhabdomyosarcoma (P < 0.001). The positive expression of rosettes strongly supports the presence of a neuroblastoma (P < 0.001). The diagnosis of Wilms' tumor is confirmed by the expression of tubules (P < 0.001). The presence of lymphoglandular bodies strongly favors the diagnosis of lymphoma (P < 0.001). While some cytologic features are highly correlated with specific SRCN, these features are not invariably present, and definitive diagnosis may require immunohistochemical or ultrastructural analysis performed on cell block material.

Carcinoma, Small Cell↗

PubMed1988

The use of regression analysis to determine hospital payment: the case of Medicare's indirect teaching adjustment.

Although the intention of Medicare policy makers was to use only "legitimate" cost differences to adjust teaching hospital payment rates under the prospective payment system (PPS), the actual calculations implicitly recognized others. In this paper I question whether these implicit costs should be passed through, and whether regression analysis was used correctly to establish reimbursement rates for hospitals under PPS. Conducting regression analyses on a more inclusive set of variables than the Health Care Financing Administration (HCFA) used to establish its adjustments, I conclude that costs in teaching hospitals rise only 3.15% for each .1 increment in the resident-to-bed ratio, far lower than HCFA's original 11.59% adjustment and substantially lower than the current adjustment of 7.7% for indirect costs.

Costs and Cost Analysis↗

PubMed2006

Regression analysis of doubly censored failure time data with frailty.

In doubly censored failure time data, the survival time of interest is defined as the elapsed time between an initial event and a subsequent event, and the occurrences of both events cannot be observed exactly. Instead, only right- or interval-censored observations on the occurrence times are available. For the analysis of such data, a number of methods have been proposed under the assumption that the survival time of interest is independent of the occurrence time of the initial event. This article investigates a different situation where the independence may not be true with the focus on regression analysis of doubly censored data. Cox frailty models are applied to describe the effects of covariates and an EM algorithm is developed for estimation. Simulation studies are performed to investigate finite sample properties of the proposed method and an illustrative example from an acquired immune deficiency syndrome (AIDS) cohort study is provided.

Acquired Immunodeficiency Syndrome↗

PubMed1996

The influence of study characteristics on the healthy worker effect: a multiple regression analysis.

The so-called 'healthy worker effect' (HWE) describes a reduced mortality rate in occupational populations. From 85 occupational cohorts of workers exposed to organic solvents, we have previously found a low weighted standardized mortality ratio (SMR) for all causes (SMR = 89.5, 95 per cent confidence interval [Cl] = 89.0-90.2). Characteristics of the cohorts were examined for association with the HWE. A multiple regression analysis revealed that, for overall deaths, the closer the comparison group, the smaller the HWE (p = 0.001); the more hazardous the potential exposures, the higher the SMR (p = 0.02); the higher the social class, the greater the HWE (p = 0.02); and the higher the rates of loss to follow up, the greater the HWE (p = 0.04). These results have shown that, in addition to time-related modifiers, the comparison group, type of occupational exposure, social class and rates of loss to follow-up significantly influence the size of the so-called HWE. Differences in the HWE related to gender and race were probably attributable to different rates of loss to follow-up.

Cohort Studies↗

PubMed1998

A regression analysis estimating the number of drug-using arrestees in 185 US cities.

OBJECTIVES: This study sought to provide population-based estimates of drug-using arrestees in the 185 largest US cities. METHODS: A prevalence model for drug-using arrestees was developed by relating selected social indicators (from 1990 census data) and drug use rates (from Drug Use Forecasting program data) via logistic regression analysis. RESULTS: It was estimated that in 1990, across the 185 cities, about 925,000 arrestees used cocaine, 317,000 used opiates, 213,000 used amphetamines, 389,000 were drug injectors, and 1,296,000 used an illicit drug. CONCLUSIONS: This approach represents a cost-efficient method for prevalence estimation based on empirically demonstrable relationships between social indicators and drug use rates.

Adolescent↗

PubMed1982

Survival with malignant melanoma: a regression analysis of prognostic factors.

A Cox's regression model for survival data has been applied to investigate which of the many clinical and histopathologic parameters have a significant influence on the survival probability of the patients with primary malignant melanoma. The thicker the tumor and the deeper the invasion, the poorer the prognosis. Localization of the tumor on the mucous membranes, ulceration, and presence of epithelioid cells are all bad prognostic signs. The stronger the rim of inflammatory cell infiltrate, the better the prognosis for the patient. Females have better prognosis than males and prognosis aggravate with age. Using these parameters it is possible to make a prognosis forecast for the individual patient. Two patients, one with a favorable set of parameters and another with an unfavorable set, are described.

Follow-Up Studies↗

PubMed2000

Regression analysis of metabolite concentrations estimated from localized proton MR spectra of active and chronic multiple sclerosis lesions.

Localized short echo time magnetic resonance (MR) spectra were obtained from patients with multiple sclerosis of relapsing-remitting or secondary chronic-progressive course and from healthy controls. Automated analysis using model spectra, sensitivity correction, and subtraction of partial ventricular volume yielded tissue concentrations of metabolites that were in line with findings of previous studies. Additional findings were increased creatine in chronic lesions and increased myo-inositol in normal-appearing white matter. Regression analysis was performed to reveal concomitant changes of metabolite concentrations. Differences in the correlations between cholines and myo-inositol suggest increased expression of myo-inositol in chronic lesions or of cholines in active, contrast-enhanced lesions. A correlation between N-acetyl-aspartate and creatine, which is probably due to extracellular edema, was observed in active but not in chronic lesions. Creatine and cholines correlated in chronic lesions, which may be the result of gliosis. The consequences of these findings for the interpretation of absolute concentrations and creatine ratios are discussed.

Acute Disease↗

PubMed2007

Regression analysis of failure time data with informative interval censoring.

Interval censoring arises when a subject misses prescheduled visits at which the failure is to be assessed. Most existing approaches for analysing interval-censored failure time data assume that the censoring mechanism is independent of the true failure time. However, there are situations where this assumption may not hold. In this paper, we consider such a situation in which the dependence structure between the censoring variables and the failure time can be modelled through some latent variables and a method for regression analysis of failure time data is proposed. The method makes use of the proportional hazards frailty model and an EM algorithm is presented for estimation. Finite sample properties of the proposed estimators of regression parameters are examined through simulation studies and we illustrate the method with data from an AIDS study.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Intraocular lens power prediction for triple procedures in Fuchs' dystrophy using multiple regression analysis.

PURPOSE: To develop a correcting term for intraocular power (IOLP) prediction for penetrating keratoplasty combined with simultaneous extracapsular cataract extraction and posterior chamber lens implantation (triple procedure). METHODS: As part of a prospective clinical study, triple procedures were performed in 42 eyes with Fuchs' dystrophy. Only eyes with readable preoperative K-values were included in this study. Differences (DEV) between achieved and target refraction (TR) depending on the values of the theoretical-optical formula according to HAIGIS were investigated using multiple regression analysis in a linear anova model: DEV = a + b CP + c AL + d IOLP + e TR. CP represents central corneal power, AL represents axial length. RESULTS: Spherical equivalent after suture removal was - 1.39 +/- 2.86 D (TR: - 1.64 +/- 1.72 D). A multiple regression formula was developed for correction of conventionally calculated IOL power. CP (b = - 1.391, p = 0.028), AL (c = - 4.733, p = 0.007), IOLP (d = - 1.301, p = 0.009) and TR (e = - 1.804, p = 0.005) correlated significantly with DEV (a = 198.684). CONCLUSION: Proposed correcting multiple regression formula for IOL power prediction may help to improve the postoperative refractive outcome in patients undergoing triple procedures.

Adult↗

PubMed1982

[Evaluation of the interrelations among auditory potential parameters by means of the technic of correlation-regression analysis].

The characteristics (amplitude, latency) of two types of evoked potentials, action potential of the 8th nerve recorded at the cochlea round window and sonomotor evoked potential recorded from the postauricular region and the back of the guinea pigs were studied in response to sound stimulation. The degree and type of interrelation between the parameters of the auditory evoked potentials were established employing the method of correlation-regression analysis. A close linear dependence was established for amplitude values ( r = 0.93) of the action potential and the sonomotor potential irrespective of the recording site of the latter. The similar dependence (r = 0.91) was established when analysing the latency of the action potential and the evoked sonomotor potential, if the latter was in the postauricular region. The performed mathematical simulation permitted justifying the correction of disturbed functions of the auditory system.

Action Potentials↗

PubMed2005

Modeling the energy content of combustible ship-scrapping waste at Alang-Sosiya, India, using multiple regression analysis.

Alang-Sosiya is the largest ship-scrapping yard in the world, established in 1982. Every year an average of 171 ships having a mean weight of 2.10 x 10(6)(+/-7.82 x 10(5)) of light dead weight tonnage (LDT) being scrapped. Apart from scrapped metals, this yard generates a massive amount of combustible solid waste in the form of waste wood, plastic, insulation material, paper, glass wool, thermocol pieces (polyurethane foam material), sponge, oiled rope, cotton waste, rubber, etc. In this study multiple regression analysis was used to develop predictive models for energy content of combustible ship-scrapping solid wastes. The scope of work comprised qualitative and quantitative estimation of solid waste samples and performing a sequential selection procedure for isolating variables. Three regression models were developed to correlate the energy content (net calorific values (LHV)) with variables derived from material composition, proximate and ultimate analyses. The performance of these models for this particular waste complies well with the equations developed by other researchers (Dulong, Steuer, Scheurer-Kestner and Bento's) for estimating energy content of municipal solid waste.

Conservation of Energy Resources↗

PubMed1992

Application form items as predictors of performance and longevity among respiratory therapists: a multiple regression analysis.

UNLABELLED: Errors in employee selection and consequent high turnover rates are expensive and can result in poor staff morale and possible harm to patients and personnel. METHOD: We investigated the predictive validity of commonly used application blank items as measures of future performance, absenteeism, tardiness, and tenure (the criterion variables) among 100 hospital-employed respiratory therapists and looked at the relationships among the criterion variables. RESULTS: Regression analysis showed the most significant predictive variables to be grade point average in respiratory therapy school, college education in addition to respiratory therapy training (particularly an associate degree in health sciences or a baccalaureate degree), and, surprisingly, the neatness of the application form itself. No important differences were found among the types of respiratory therapy program attended or the length of previous respiratory therapy experience. CONCLUSION: The data offer cautious evidence for the validity of some application items to predict some employee behaviors. The relatively low correlations among the criterion variables (absenteeism, tardiness, tenure, and performance) suggest that these items may be assessing substantially different aspects of employee behavior.

Absenteeism↗

PubMed1992

Moderated regression analysis and Likert scales: too coarse for comfort.

One of the most commonly accepted models of relationships among three variables in applied industrial and organizational psychology is the simple moderator effect. However, many authors have expressed concern over the general lack of empirical support for interaction effects reported in the literature. We demonstrate in the current sample that use of a continuous, dependent-response scale instead of a discrete, Likert-type scale, causes moderated regression analysis effect sizes to increase an average of 93%. We suggest that use of relatively coarse Likert scales to measure fine dependent responses causes information loss that, although varying widely across subjects, greatly reduces the probability of detecting true interaction effects. Specific recommendations for alternate research strategies are made.

Adult↗

PubMed2005

Distinguishing dengue fever from other infections on the basis of simple clinical and laboratory features: application of logistic regression analysis.

BACKGROUND: Dengue fever is a frequent cause of admission to hospital in South East Asia, however many of the clinical characteristics and abnormalities on laboratory investigations at presentation are found in other common infections. OBJECTIVES: To describe the clinical and laboratory features of dengue fever and other common febrile illnesses in Singapore. STUDY DESIGN: We performed a prospective study of consecutive adult admissions to an infectious diseases hospital. Logistic regression analysis was used to identify symptoms, physical signs and laboratory features that differentiated dengue fever from other febrile illnesses within the first 2 days of admission. RESULTS: Of the 381 patients studied, 148 had serologically confirmed dengue fever. Most of these had uncomplicated dengue fever, and only 9% had dengue haemorrhagic fever. A model based on clinical features alone (including a variety of cutaneous signs, pulse rate and the presence of pharyngeal injection) was able to differentiate dengue fever from other infections with a sensitivity of 74% and specificity of 79%. A model based on clinical features (rash) and laboratory parameters (white cell count, haemoglobin, prothrombin time, creatinine and bilirubin levels), achieved a sensitivity of 84% and specificity of 85%. CONCLUSIONS: A combination of simple clinical and laboratory parameters are potentially able to predict dengue fever with a high level of accuracy in adults presenting to hospital with febrile illnesses in Singapore.

Adult↗

PubMed1999

Outcome of tuberculous meningitis at 6 and 12 months: a multiple regression analysis.

OBJECTIVE: There are few studies on the long-term outcome of tuberculous meningitis (TBM) employing multivariate analysis. The present study was undertaken to evaluate the outcome predictors of TBM at 6 and 12 months. METHOD: Those patients with TBM who could be sequentially followed up for 6 and 12 months were included in this prospective, hospital-based study. The outcome was defined at 6 and 12 months by Barthel Index (BI) score into complete (BI = 20), partial (BI = 12-19) and poor (BI<12). Death was included in the 'poor recovery' group for statistical analysis. A number of clinical, laboratory and radiological parameters were evaluated by multiple regression analysis. RESULTS: Fifty-eight patients with TBM aged between 1 and 64 years (mean 25.6 years), 18 of whom were females and 17 children below 12 years, were included in the study. Fifty-eight patients were followed up for 6 months and 56 for 12 months. At 6 months' follow-up 37 patients had complete recovery, three partial, six poor and 12 had died. At 12 months, 40 patients had complete recovery, one partial and three poor. The best set of parameters predicting outcome at 6 and 12 months included stage of TBM, Glasgow coma scale (GCS) and brain infarction. CONCLUSION: This study highlights the importance of stage of meningitis, GCS and infarction in predicting the long term outcome of tuberculous meningitis.

Adolescent↗