SEARCH · PubMed Health

Results for “Regression Analysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources

PubMed2000

Assessment of aortic line of elasticity using polynomial regression analysis.

BACKGROUND: The aim of this study was to assess the sigmoid line of elasticity in the human aorta. METHODS AND RESULTS: The pressure-diameter relation was measured in the descending aorta in 120 subjects. In an additional group of 6 subjects, transient vena caval occlusion produced 5 sets of pressure-diameter data. We found that the best fit curve of the pooled pressure-diameter data was a third-order polynomial. A polynomial equation was used to calculate the sigmoid line of elasticity in the entire population and after the administration of diltiazem (15 patients) or enalaprilat (10 patients). The sigmoid line of elasticity was significantly different with respect to age (P<0.001), history of hypertension (P<0.004), and hypercholesterolemia (P<0.02). The difference between the transition point and the peak systolic pressure was increased in normal subjects compared with patients (P<0.0001). The sigmoid line shifted leftward and upward with diltiazem, but it remained unchanged with enalaprilat. During an average of 3 years of follow-up, 19 of 88 patients developed stroke (n=4), unstable angina (n=8), acute myocardial infarction (n=4), or acute pulmonary edema (n=3). CONCLUSIONS: This approach provides a quantitative evaluation of the aortic line of elasticity, which can differentiate the intrinsic from the extrinsic aortic elastic properties. Furthermore, it is a powerful and independent risk factor for cardiovascular events.

Aorta↗

PubMed2002

Strategies to improve neuroreceptor parameter estimation by linear regression analysis.

In an attempt to improve neuroreceptor distribution volume (V) estimates, the authors evaluated three alternative linear methods to Logan graphical analysis (GA): GA using total least squares (TLS), and two multilinear analyses, MA1 and MA2, based on mathematical rearrangement of GA equation and two-tissue compartments, respectively, using simulated and actual PET data of two receptor tracers, [(18)F]FCWAY and [(11)C]MDL 100,907. For simulations, all three methods decreased the noise-induced GA bias (up to 30%) at the expense of increased variability. The bias reduction was most pronounced for MA1, moderate to large for MA2, and modest to moderate for TLS. In addition, GA, TLS, and MA1, methods that used only a portion of the data (T > t*, chosen by an automatic process), showed a small underestimation for [(11)C]MDL 100,907 with its slow kinetics, due to selection of t* before the true point of linearity. These noniterative methods are computationally simple, allowing efficient pixelwise parameter estimation. For tracers with kinetics that permit t* to be accurately identified within the study duration, MA1 appears to be the best. For tracers with slow kinetics and low to moderate noise, however, MA2 may provide the lowest bias while maintaining computational ease for pixelwise parameter estimation.

Basal Ganglia↗

PubMed2003

Optimization of submerged-culture conditions for mycelial growth and exo-biopolymer production by Auricularia polytricha (wood ears fungus) using the methods of uniform design and regression analysis.

This paper is concerned with the optimization of submerged culture conditions for mycelial growth and exo-biopolymer production by Auricularia polytricha by one-factor-at-a-time and uniform design (UD) methods. First, the one-factor-at-a-time method was adopted to investigate the effects of environmental factors (i.e., initial pH and temperature) and variables of medium components (i.e., carbon, nitrogen and mineral sources) on mycelial growth and exo-biopolymer production. Sucrose, yeast extract, and K2HPO4 were identified to be the most suitable carbon, nitrogen, and mineral sources, respectively. The optimal temperature and initial pH for mycelial growth and exo-biopolymer production were found to be 25 degrees C and 5.0, respectively. Subsequently, the concentrations of sucrose, yeast extract, and K2HPO4 were optimized using the UD method. The optimal concentrations for the enhanced production were determined as 6% (w/v) sucrose, 2.5% (w/v) yeast extract, and 0.3% (w/v) K2HPO4 for mycelial yield, and 6% (w/v) sucrose, 1.28% (w/v) yeast extract, and 0.3% (w/v) K2HPO4 for exo-biopolymer production, respectively. Subsequent experiments confirmed the validity of the models. This optimization strategy in shake-flask culture led to a mycelial yield of 6.14 g/l, and exo-biopolymer production of 2.12 g/l, respectively, which were considerably higher than those obtained in the preliminary studies. By using the optimized medium, the maximum concentrations of mycelial biomass and exo-biopolymer in a 5 litre stirred-tank bioreactor indicated 35.3 g/l and 3.1 g/l, respectively.

Basidiomycota↗

PubMed1983

Multiple regression analysis of risk factors for cardiovascular disease and cancer mortality in Busselton, Western Australia--13-year study.

The mortality of 1564 Busselton subjects has been studied from 1966-79 to determine whether risk factors for cardiovascular disease (CVD) and coronary heart disease (CHD) showed any change in emphasis compared with the Framingham Population Study of 20 yr previously. The Busselton analysis used subjects free of probable and suspect coronary heart disease at onset. In men aged 40-59, systolic blood pressure (SBP), forced expiratory volume (FEV), and serum cholesterol levels were significant independent determining variables for CVD mortality and cholesterol for CHD mortality, with SBP being related to CVD in men aged 60-74 yr. In women, there were few indicators of future vascular risk with no significant determining variable for CVD and CHD in 40-59 yr olds, but blood glucose and FEV were significant risk factors for CVD in women aged 60-74 yr. Cholesterol was unrelated to mortality in women but showed negative relationship with cancer in 60-74 yr old men. In total mortality, smoking in men and women, and obesity in women were significant risk factors; 1 hr serum insulin had a negative relationship in men aged 40-59 yr, and a stronger positive relationship in men aged 60-74 yr, but this may have been due to the close negative association of the variable with body size (i.e. height). More studies are required to ascertain whether glucose and insulin have an aetiological role in vascular disease.

Adult↗

PubMed2001

Immunohistochemical panels for differentiating epithelial malignant mesothelioma from lung adenocarcinoma: a study with logistic regression analysis.

Immunohistochemistry provides an important indicator for differential diagnosis between pleural malignant mesothelioma and lung adenocarcinoma, which have complex therapeutic and medicolegal implications. To pinpoint a reliable, restricted panel of markers, the authors evaluated the efficacy of select commercial antibodies in a series of patients with confirmed clinicopathologic diagnosis of mesothelioma or lung adenocarcinoma with the aid of multiple logistic classification tables. Specimens of 46 mesotheliomas and 20 lung adenocarcinomas were examined with calretinin, thrombomodulin, cytokeratins (CKs) 5/6, and high-molecular weight CKs (indicators of mesothelioma), alongside MOC 31, Ber-EP4, and carcinoembryonic antigen (CEA; indicators of lung adenocarcinoma). Of the mesotheliomas, 40 of 46 (87%) were positive with calretinin, 29 of 46 (63%) with thrombomodulin, 40 of 46 (87%) with CKs 5/6, and 41 of 46 (89%) with high-weight CKs; five of 46 mesotheliomas (11%) were focally reactive with MOC 31, four of 46 (9%) with Ber-EP4, and two of 46 (4%) with CEA. Of the lung adenocarcinomas, 18 of 20 (90%) were positive with MOC 31, 20 of 20 (100%) with Ber-EP4, and 17 of 20 (85%) with CEA; and two of 20 (10%) were focally reactive with calretinin, one of 20 (5%) with thrombomodulin, none of 20 (0%) with CKs 5/6, and five of 20 (25%) with high-weight CKs. Multiple logistic modeling indicated two batteries of three antibodies permitting more than 98% overall accuracy: Ber-EP4 plus CKs 5/6 plus calretinin, and Ber-EP4 plus CKs 5/6 plus CEA.

Adenocarcinoma↗

PubMed1999

Interpreting age, period and cohort effects in plasma lipids and serum insulin using repeated measures regression analysis: the CARDIA Study.

Observed changes in health-related behaviours and disease risk factors may arise from physiological or environmental changes, or from biases due to sampling or measurement errors. We illustrate problems in the interpretation of such changes with longitudinal data from the Coronary Artery Risk Development in Young Adults (CARDIA) study. Mean plasma cholesterol was 14 mg/dl higher in 27- than in 20-year-old black men cross-sectionally, but longitudinally it declined by 4 mg/dl during the 7 years. To sort out these contradictory assessments of the effect of age/passage of time, we estimated age and period effects under the assumptions that age effects are a smooth function of age independent of period, and that period effects are changes common to persons across all ages. Simple estimates the age effect, such as the cross-sectional age slopes, may be confounded by cohort effects, by interactions of time and age after baseline, or by the occurrence of non-linearities in response after baseline. We note examples of each potential type of bias. The data and background literature support the assumption that cohort effects do not seriously compromise interpretation for these variables in the CARDIA study. Strong secular decreases in plasma cholesterol, apparently due to population-wide dietary change, mask increases with ageing. Age increases in triglycerides are largely explained by increases in body fatness. For these data, we cautiously accept the cross-sectional age slope as an estimate of ageing and the age-matched time trend as an estimate of secular trend.

Adolescent↗

PubMed2005

Complexity of program and clinical outcomes of heart failure disease management incorporating specialist nurse-led heart failure clinics. A meta-regression analysis.

OBJECTIVES: To determine whether a hierarchy of effectiveness exists with respect to complexity of published protocols of heart failure (HF) disease management (DM) incorporating specialist nurse-led HF clinics. DATA SOURCES AND STUDY SELECTION: We searched MEDLINE (1966-November 2004), the Cochrane Library, article bibliographies, and contacted experts. Inclusion criteria were random allocation of at least 100 patients, specialist HF nurses, HF clinics, and readmission as an outcome measure. DATA EXTRACTION: Paired reviewers conducted quality assessment, deconstructed and categorized protocols by complexity, and extracted results for readmission, mortality, the combined endpoint of mortality and hospitalization, HF readmission, and hospital days utilized. DATA SYNTHESIS: Six trials were selected (N=949, mean age 73 years [range 62-79], men 58%, LVEF 34% [27-41], and average follow-up of 8.5 months [3-12]). Compared with usual care, the overall relative risk [95% confidence interval] for readmission with this strategy was 0.91 [0.72, 1.16], mortality was 0.80 [0.57, 1.06], and the combined endpoint of mortality and hospitalization was 0.88 [0.74, 1.04]. We observed better outcomes for programs with versus programs without hospital discharge planning and immediate post-discharge follow-up; readmission 0.30 [0.04, 2.60] vs. 1.00 [0.86, 1.17], mortality 0.96 [0.63, 1.47] vs. 0.75 [0.55, 1.03], the combined endpoint of mortality and hospitalization 0.61 [0.18, 2.02] vs. 0.91 [0.80, 1.03], HF readmission 0.09 [0.10, 0.65] vs. 0.65 [0.43, 1.00], and hospitalized days utilized per patient -0.26 [-0.49,-0.02] vs. 0.09 [-1.17, 1.34]. CONCLUSIONS: HF DM with specialist nurse-led HF clinics is a promising strategy or effective alternative whose benefit may be optimized by programs with a homogeneous structure and components that are delivered with consistency.

Aged↗

PubMed2006

Comprehensive regression analysis of hepatitis B virus X antigen level and anti-HBx antibody titer in the sera of patients with HBV infection.

Although the pathogenetic significance of hepatitis B virus x protein (HBxAg) in chronic hepatitis, liver cirrhosis, and primary hepatocellular carcinoma has already been studied, the comparative analyses of both the actual serum HBxAg levels and antibody production against various HBx epitopes have been examined to lesser extent. We have simultaneously investigated the relationship between antibody production (IgG and IgM) against the HBxAg fragments and HBxAg level in the sera of patients with acute (14) or chronic hepatitis (80) and symptomless carriers (12). A recently developed sandwich-type ELISA was used for the quantitative measurements of HBxAg. Overlapping recombinant and synthetic antigens were used to map the fine epitope specificities of circulating anti-HBx antibodies. In acute hepatitis, we have found high and homogenous correlation in the IgM type immune responses against all the examined HBxAg regions. Moreover, strong correlation has been observed between IgG type immune responses to a characteristic C-terminal region (C1: 79-117) and the longest fragment (X: 10-143). Moderate correlation has been found between HBxAg concentration and the IgG type anti-HBx antibody levels against C-terminus of HBxAg in patients with chronic hepatitis. In the case of symptomless carriers, there were also demonstrable associations in the immune responses against the C-terminal sequences; however, significant correlations were found for antibody production against the N-terminal region as well. The examinations show that the C-terminal sequence, responsible for transactivation, promotes an efficient IgG antibody response in all three groups of patients, whereas the negative regulator N-terminal part of the HBxAg molecule for the most part does not trigger antibody production. This suggests that the immune responses against various - biologically active - epitopes of the HBxAg may have a different role in the pathogenesis of hepatitis and may be used as prognostic markers in human HBV infections.

Amino Acid Sequence↗

PubMed2001

Recent decline in cancer mortality in Catalonia (Spain). A joinpoint regression analysis.

The aim of this paper was to analyse recent changes in cancer mortality in Catalonia (Spain) between 1975 and 1998 using joinpoint regression models. Mortality data were obtained from the Mortality Registry of Catalonia. For each sex, age-standardised (standard world population) mortality rates were computed by the direct method, and joinpoint analysis was used to identify the best fitting points where a statistically significant change in the rates had occurred. In men, the overall cancer mortality (except skin non-melanoma) was highest in 1991 and decreased thereafter. Lung cancer was the main cause of cancer mortality, with an increase until 1989, and a subsequent levelling off (-0.8% annual between 1989 and 1998). Colorectal cancer was the second cause of cancer death, both in men and women, with a levelling-off of the rates since 1991 and 1989, respectively. In women, the mortality rate decreased for total cancer (except skin non-melanoma) since 1991 (-0.9% annually). Breast cancer increased until 1975, levelled-off and begun to decline since 1992 (-3.8% annual). Lung cancer increased since 1988 (+2.1%) and became the third cancer cause of death among women in 1998. These changes are mainly due to the decline of smoking prevalence in males, but not in females, and to the introduction of new diagnostic techniques and improved therapies for female breast cancer.

Adult↗

PubMed2003

Factors determining the post-operative hypo-albuminaemia in cancer patients--stepwise regression analysis.

AIM: To investigate factors influencing post-operative hypo-albuminaemia in cancer patients, with special reference to low dose albumin and/or immunoglobulins administration. PATIENTS AND METHODS: In 270 patients with malignant neoplasms, who underwent extensive chest and/or abdominal surgery, albumin concentrations on the first four postoperative days were examined. One hundred and three high-risk patients received human immunoglobulins intravenously; 44 were given albumin. Univariate and multivariate regression analyses were used to determine the factors influencing albuminaemia on the first four postoperative days. RESULTS: Mean nadir of hypo-albuminaemia occurred on the third postoperative day. In the multivariate analysis, a positive correlation was found between postoperative albuminaemia and pre-operative albuminaemia (b = 0.4919; p = 0.0000) as well as male gender (b = 2.0939; p = 0.0025). A negative correlation was found with the duration of surgery (b = -0.0416; p = 0.0212), pre-operative plasma protein (b = -0.2118, p = 0.0130) and postoperative immunoglobulin administration (b = -1.8858, p = 0.0074). CONCLUSIONS: Postoperative albuminaemia is positively correlated with pre-operative albuminaemia and male gender and negatively correlated with the duration of surgery, pre-operative proteinaemia and postoperative Ig administration.

Aged↗

PubMed2004

[Dose-volume histogram regression analysis of uveal melanomas after single fraction gamma knife radiosurgery].

BACKGROUND: To evaluate tumor regression and sequelae in 30 uveal melanomas treated with Gamma Knife radiosurgery between 1992 and 1995 at the Gamma Knife center in Graz. PATIENTS: A total of 30 uveal and ciliary body melanomas were treated with a single fraction of the Gamma Knife. The mean marginal dose was 52.1 Gy, (median 50 Gy). Of the tumors, 15 were large (higher than 8 mm), 14 were medium sized (3-8 mm) and one was a small melanoma (<3 mm). Among them were 6 juxtapapillary, 10 (juxta-) maculary melanomas, 5 tumors located in the midperiphery and 9 ciliary body melanomas. METHOD: Dose-volume histogram analysis. RESULTS: After a maximum follow up of 9 years and 7 months, 8 tumors regressed into a scar, 17 tumors into a residual prominence between 50% and 80% of the initial tumor height, 3 tumors showed no change and in 2 patients recurrence was obvious. Sequelae were classified as mild (in 3 patients), moderate (3), severe (5) and very severe (19). CONCLUSIONS: Significant factors for the development of severe sequelae were the tumor volume and the marginal dose, the mean dose proved to be more important than the marginal dose and the irradiated volume more important than the selective critical dose.

Adult↗

PubMed1982

Cefoperazone: regression analysis, disk content, and disk susceptibility testing considerations.

Cefoperazone agar dilution minimal inhibitory concentration (MIC) susceptibility results were compared with zones of inhibition produced by disk diffusion susceptibility testing. Disks containing 30, 50, 75, and 100 micrograms of cefoperazone were tested for purposes of regression line comparisons and error rate-bounded analysis. Results suggest that if the MIC equivalent of susceptibility is 32 micrograms/ml, either a 50-micrograms disk with zone sizes of susceptibility (S) greater than or equal to 15 mm and resistance (R) less than or equal to 12 mm or a 75-micrograms disk with zone sizes of S greater than or equal to 17 mm and R less than or equal to 14 mm may be appropriate. If the MIC equivalent of susceptibility is 64 micrograms/ml, this would dictate use of a 75-micrograms disk with zone sizes of S greater than or equal to 17 mm and R less than or equal to 12 mm. Disks containing either less than or equal to 30 or greater than or equal to 100 micrograms of cefoperazone did not adequately discriminate among susceptible and resistant bacterial strains at either the 32- or 64-micrograms/ml MIC equivalent.

Anti-Bacterial Agents↗

PubMed2000

Linear regression analysis of censored medical costs.

This paper deals with the problem of linear regression for medical cost data when some study subjects are not followed for the full duration of interest so that their total costs are unknown. Standard survival analysis techniques are ill-suited to this type of censoring. The familiar normal equations for the least-squares estimation are modified in several ways to properly account for the incompleteness of the data. The resulting estimators are shown to be consistent and asymptotically normal with easily estimated variance-covariance matrices. The proposed methodology can be used when the cost database contains only the total costs for those with complete follow-up. More efficient estimators are available when the cost data are recorded in multiple time intervals. A study on the medical cost for ovarian cancer is presented.

Journal Article↗

PubMed1978

Panel studies of acute health effects of air pollution. II. A methodologic study of linear regression analysis of asthma panel data.

Panel studies relating illness, such as asthma attacks, cardiopulmonary symptoms, and acute respiratory symptoms, to daily air pollution and weather are important in environmental epidemiology. A study of the practical robustness of multiple linear regression procedures, which have been the preferred statistical models in analyses, is presented. The study is based on data from three asthma panels in Chattanooga, Tennessee, collected in 1972-1973. Linear regression models, commonly used, which incorporate only minimum temperature and an air pollutant were found to be potentially misleading; such models are highly sensitive to reporting trends in the data and do not correct adequately for weather variables. Temporal and spatial control strategies were employed and proved to be useful in detecting problems in the data due to undiscovered intervening variables. True day-to-day relationships estimated by a pair-day analysis were frequently inconsistent with "daily" effects estimated by the usual regression models and suggested that, in fact, the asthma panel data contained no useful information concerning day-to-day relationships.

Adolescent↗

PubMed1976

Regression analysis of the log odds ratio: a method for retrospective studies.

Quantification of the dependence of the odds ratio on concomitant variables associated with each of several 2 X 2 tables, using a regression model proposed by Zelen [1971], is an important tool for retrospective studies in epidemiology, An "exact" analysis may be based on the conditional likelihood obtained by fixing all the marginal totals. A symptotically this approach is equivalent to use of an unconditional log-linear model. The method is used to reanalyze data reported by Kneale [1971] on the relationship between obstetric radiation and childhood cancer.

Biometry↗

PubMed2001

Data preprocessing and partial least squares regression analysis for reagentless determination of hemoglobin concentrations using conventional and total transmission spectroscopy.

Visible-near infrared spectroscopy was successfully used for the determination of total hemoglobin concentration in whole blood. Absorption spectra of whole blood samples, whose hemoglobin concentrations ranged between 6.6 and 17.2 g/dL, were measured from 500 to 800 nm. Two different types of transmission were measured: conventional transmission spectroscopy which collected primarily collimated radiation transmitted through the sample, and total transmission spectroscopy which used an integrating sphere to collect all scattered light as well. Different preprocessing techniques in conjunction with a partial least squares regression calibration model to predict hemoglobin concentrations were applied to the above two types of transmission. Depending on different preprocessing methods, the standard error of predictions ranged from 0.37 to 2.67 g/dL. Mean centering gave the most accurate prediction in our particular data set. Preprocessing methods designed for compensation of the scattering effect produced the worst results contrary to expectations. For univariate analysis, better prediction was achieved by total transmission measurement than by conventional transmission measurement. No significant difference was observed for multivariate analysis on the other hand. Careful selection of the data preprocessing methods and of the multivariate statistical model is required for reagentless determination of hemoglobin concentration in whole blood.

Hemoglobins↗

PubMed2003

Semiparametric regression analysis of longitudinal data with informative drop-outs.

Informative drop-out arises in longitudinal studies when the subject's follow-up time depends on the unobserved values of the response variable. We specify a semiparametric linear regression model for the repeatedly measured response variable and an accelerated failure time model for the time to informative drop-out. The error terms from the two models are assumed to have a common, but completely arbitrary joint distribution. Using a rank-based estimator for the accelerated failure time model and an artificial censoring device, we construct an asymptotically unbiased estimating function for the linear regression model. The resultant estimator is shown to be consistent and asymptotically normal. A resampling scheme is developed to estimate the limiting covariance matrix. Extensive simulation studies demonstrate that the proposed methods are suitable for practical use. Illustrations with data taken from two AIDS clinical trials are provided.

Child↗

PubMed1987

[Evaluation by multiple regression analysis of factors influencing the chemosensitivity of human tumors xenografted into nude mice].

The chemosensitivity of human cancer lines is thought to be expressed as a result of contributions by various interacting factors. Multiple regression analyses were performed in order to clarify the weighting of factors responsible for the chemosensitivity of 15 human cancers xenografted into nude mice. Inhibition rates of 11 anticancer agents predetermined for each line of human cancer were used as the criterion variables. As the explanatory variables, 9 parameters characteristic of each cancer or cancer-bearing mouse were selected as follows; grade of differentiation, vascularity, percentage necrosis, volume doubling time, labeling index, LDH activity, tissue/serum LDH ratio, thymidine phosphorylase activity and serum CEA. By applying this analysis with stepwise deletion, the estimated multiple regression equations for drug sensitivity were clarified for each drug. Although all equations were composed of different factors and their partial repression coefficients varied from drug to drug, those among analogous drugs such as FT-207 and UFT, or MMC and M-83 had similar factors. The equations for M-83, ACNU and ADR consisted of a number of parameters with a sufficiently high coefficient of determination of over 80%. Even in cases of MXT that showed no significant factor upon simple correlation analysis, an equation with 7 factors revealed a coefficient of determination of 0.83. The estimated values of effectiveness for these drugs showed remarkable coincidence with each actual value. For some drugs, the in vivo mode of action was inferred through this analysis.

Animals↗