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PubMed2002

Automation of a procedure to find the polynomial which best fits (kappa, c1, c2, T) data of electrolyte solutions by non-linear regression analysis using MATHEMATICA software.

A MATHEMATICA package, 'CONDU.M', has been developed to find the polynomial in concentration and temperature which best fits conductimetric data of the type (kappa, c, T) or (kappa, c1, c2, T) of electrolyte solutions (kappa: specific conductivity; ci: concentration of component i; T: temperature). In addition, an interface, 'TKONDU', has been written in the TCL/Tk language to facilitate the use of CONDU.M by an operator not familiarised with MATHEMATICA. All this software is available on line (UPV/EHU, 2001). 'CONDU.M' has been programmed to: (i) select the optimum grade in c1 and/or c2; (ii) compare models with linear or quadratic terms in temperature; (iii) calculate the set of adjustable parameters which best fits data; (iv) simplify the model by elimination of 'a priori' included adjustable parameters which after the regression analysis result in low statistical significance; (v) facilitate the location of outlier data by graphical analysis of the residuals; and (vi) provide quantitative statistical information on the quality of the fit, allowing a critical comparison among different models. Due to the multiple options offered the software allows testing different conductivity models in a short time, even if a large set of conductivity data is being considered simultaneously. Then, the user can choose the best model making use of the graphical and statistical information provided in the output file. Although the program has been initially designed to treat conductimetric data, it can be also applied for processing data with similar structure, e.g. (P, c, T) or (P, c1, c2, T), being P any appropriate transport, physical or thermodynamic property.

Journal Article↗
PubMedDate not supplied

Logistic regression analysis of low grade spindle cell lesions. A cytologic study.

OBJECTIVE: To identify key diagnostic cytologic criteria for various low grade spindle cell lesions. STUDY DESIGN: We reviewed 20 synovial sarcomas, 18 benign neural tumors, 10 reparative lesions, 24 other benign and 27 additional malignant low grade spindle cell lesions. All specimens were coded as to the presence or absence of the following variables: high cellularity, tissue fragments, tissue culture appearance, epithelial fragments, vessel fragments, vascular arcades, fibrillar ground substance, myxoid background, microcystic areas, parallel arrangement of nuclei, naked nuclei, single cells, binucleate cells, multinucleate cells, long filamentous cells, short spindle cells, stellate cells, lipoblasts, nuclear pleomorphism, nuclei with pointed ends, comma/fishhook nuclei, cigar-shaped nuclei, ovoid/round nuclei, small nucleoli, large nucleoli, mitotic figures, intranuclear vacuoles and background histiocytes. A logistic regression analysis was performed to identify the variables predictive of malignant lesions, specifically synovial sarcomas, benign neural tumors and reparative lesions. RESULTS: Statistical analysis selected high cellularity, short spindle cells, small nucleoli and absence of tissue culture appearance as the main criteria for malignant neoplasms. Tissue fragments and high cellularity were selected as the primary criteria and absence of long filamentous cells and of myxoid background as the secondary criteria for synovial sarcomas. It selected fibrillar ground substance and absence of ovoid/round nuclei as the key criteria for benign neural tumors. The presence of a tissue culture appearance was the major criterion for reparative lesions. CONCLUSION: There are many previously described cytologic criteria, but we found that when subjected to statistical analysis, only a few features were significant in the evaluation of low grade spindle cell lesions.

Biopsy↗
PubMed1995

Prediction of progression of the curve in girls who have adolescent idiopathic scoliosis of moderate severity. Logistic regression analysis based on data from The Brace Study of the Scoliosis Research Society.

In a study conducted by the Scoliosis Research Society, 159 girls with a mean age of thirteen years (range, ten to fifteen years) who had adolescent idiopathic scoliosis were followed prospectively until skeletal maturity or until the curve had increased 6 degrees or more. All patients had had an initial curve of 25 to 35 degrees and an apical level between the eighth thoracic and first lumbar vertebrae, inclusive. Of the 159 patients, 120 were observed without treatment and thirty-nine were managed with lateral electrical surface stimulation. The curve progressed at least 6 degrees in eighty patients. There was no apparent difference in the outcome between the patients who were managed with observation only and those who were given electrical stimulation. Logistic regression analysis was performed to determine which of eleven factors were predictive of progression of the scoliotic curve. A Risser sign of 0 or 1, an apical level cephalad to the twelfth thoracic vertebra, and an imbalance of ten millimeters or less were found to be independently prognostic of progression of more than 6 degrees. A prognostic model that included these three factors and chronological age allowed correct classification of the curve as either progressive or non-progressive in 81 per cent of these patients who had a thoracic or thoracolumbar adolescent idiopathic scoliosis. The positive predictive value was 82 per cent, the negative predictive value was 80 per cent, and the sensitivity and specificity were each 81 per cent.

Adolescent↗
PubMed2003

Population pharmacokinetic and pharmacodynamic modeling of etanercept using logistic regression analysis.

OBJECTIVE: Our objective was to develop a population pharmacokinetic and pharmacodynamic model of etanercept in patients with rheumatoid arthritis, with the American College of Rheumatology response criterion of 20% improvement (ACR20) used as a binary clinical outcome variable. METHODS: Concentration-time profiles from 25 subjects, administered 25 mg subcutaneous etanercept twice weekly for 24 weeks, were pooled with data from 77 subjects, enrolled in a 24-week, randomized, double-blind study comparing 25 mg and 50 mg subcutaneous etanercept twice weekly. The cumulative area under the concentration-time curve (AUC) was used as the exposure variable, and ACR20 was the binomial clinical outcome. ACR20 data from another 80 placebo-treated patients enrolled in a randomized, double-blind phase III study were used to describe the placebo time course of ACR20. A logistic regression analysis with NONMEM was applied to describe the exposure-response relationship, and the 95% confidence intervals (95% CIs) were constructed by bootstrapping 1000 times. RESULTS: The population mean apparent clearance was 0.117 L/h (95% CI, 0.108-0.130 L/h) for white female patients and 0.138 L/h (95% CI, 0.118-0.163 L/h) for white male patients. Interindividual variability and interoccasion variability were 41.1% and 27.6%, respectively. The mean absorption half-life was 20.9 hours, and the elimination half-life was 95.4 hours. An improved response profile in male patients was shown, but the multiplicative factor between slope on cumulative AUC between male and female patients was not statistically significant (1.69; 95% CI, 0.37-9.99). The model-predicted percentage of patients achieving ACR20 at 6 months after dosing of 25 mg subcutaneously twice weekly was 54.9%, comparable to the observed 52.9%. CONCLUSION: The population pharmacokinetic analysis confirmed that etanercept is slowly absorbed and eliminated after subcutaneous administration. The logistic model linking cumulative AUC with ACR20 adequately characterized the time course of clinical improvement in patients with rheumatoid arthritis receiving etanercept.

Area Under Curve↗
PubMed2001

Clarithromycin resistance, but not CYP2C-19 polymorphism, has a major impact on treatment success in 7-day treatment regimen for cure of H. pylori infection: a multiple logistic regression analysis.

Mutations in the gene encoding the CYP2C-19 enzyme for PPI metabolism have been shown to enhance the chance for a cure in a H. pylori-positive patients using a two-week dual-therapy regimen involving omeprazole and amoxicillin. However, the impact of CYP2C-19 genetic polymorphism on eradication rates of a one-week triple-therapy regimen has not been examined. In this cohort study, 156 H. pylori-positive peptic ulcer or NUD patients who presented to our university hospital were recruited. They were treated by one-week omeprazole-amoxicillin-clarithromycin therapy. Host and bacterial predictive factors including H. pylori susceptibility and CYP2C-19 genotyping, as well as cure rate for H. pylori infection, were studied. Cure rate was 85.9% (95% CI: 79-91%) on an intent to treat (ITT) basis. By multiple logistic regression analysis, only clarithromycin resistance had a significant impact on treatment success (odds ratio 28.7: 95% CI: 6-172). CYP2C-19 genetic polymorphism was not associated with a significant change in cure rate. These observations indicate only clarithromycin susceptibility, not CYP2C-19 polymorphism, has a major impact on the treatment success when using a seven-day OAC H. pylori treatment regimen.

Amoxicillin↗
PubMed1998

Logistic regression analysis of myxoid sarcomas: a cytologic study.

The objective of this study was to identify key diagnostic cytologic criteria for the most common myxoid sarcomas studied by fine-needle aspiration cytology. We reviewed 27 myxoid malignant fibrous histiocytomas, 8 chordomas, 16 chondrosarcomas, and 12 myxoid liposarcomas in which both cytologic specimens and final histopathologic diagnoses were available. All specimens were coded as to the presence or absence of the following variables: high cellularity, low cellularity, tissue fragments, epithelial fragments, pale/loose ground substance, dense ground substance, chondroid fragments, large amount of myxoid material, small amount of myxoid material, capillary vessel networks, pleomorphism, binucleate cells, multinucleate cells, physaliphorous cells, cells in lacunae, signet ring cells, lipoblasts, fibroblast-like cells, histiocyte-like cells, stellate cells, long filamentous cells, short spindle cells, osteoclastic giant cells, nuclei with pointed ends, nuclei with cigar-shaped ends, fish-hook nuclei, round/ovoid nuclei, naked nuclei, large nucleoli, small nucleoli, mitotic figures, abnormal mitotic figures, intracytoplasmic hemosiderin deposits, background cells, fat, cytoplasmic vacuoles, and pleomorphic giant cells. A logistic regression analysis was performed to identify the variables predictive of myxoid malignant fibrous histiocytoma, chordoma, myxoid chondrosarcoma, and myxoid liposarcoma. The statistical analysis selected pleomorphic giant cells and the presence of fibroblast-like cells as most predictive of malignant fibrous histiocytoma, physaliphorous cells as most closely associated with chordoma, chondroid fragments as most predictive of chondrosarcoma, and lipoblasts as most predictive of liposarcoma. While myxoid lesions have many overlapping cytologic features, key criteria including the presence of lipoblasts, physaliphorous cells, chondroid fragments, and pleomorphic giant cells are useful in subclassifying these neoplasms.

Adipocytes↗
PubMedDate not supplied

Logistic regression analysis of high grade spindle cell neoplasms. A fine needle aspiration cytologic study.

OBJECTIVE: To identify primary diagnostic cytologic criteria for various high grade spindle cell neoplasms. STUDY DESIGN: We reviewed 30 osteosarcomas, 29 malignant fibrous histiocytomas (MFH), 26 malignant melanomas, 13 chondrosarcomas, 12 leiomyosarcomas, 7 angiosarcomas and 5 liposarcomas. All specimens were coded as to the presence or absence of the following variables: high or low cellularity, tissuelike fragments, glandlike fragments, single cells, binucleated cells, multinucleated cells, lipoblastlike cells, histiocytelike cells, fibroblastlike cells, signet-ring cells, short spindle cells, long filamentous cells, stellate cells, osteoclastic giant cells, malignant giant cells, background cells, pointed nuclei, cigar-shaped nuclei, fishhook-shaped nuclei, round or ovoid nuclei, intranuclear vacuoles, macronucleoli, small nucleoli, mitotic figures, abnormal mitotic figures, pleomorphism, nuclear/cytoplasmic ratio (mild, moderate, marked increase), amount of cytoplasm (scant, moderate, abundant), fine or coarse granular cytoplasm, intracytoplasmic hemosiderin deposits, melanin, cytoplasmic vacuoles, fat, capillary vessel fragments, storiform pattern, necrosis, large or small amount of myxoid material, filamentous stroma, dense collagenous stroma, osteoid, chondroid and cells in lacunae. A logistic regression analysis was performed to identify the variables predictive of each diagnostic category. RESULTS: The statistical analysis selected positive expression of osteoid, osteoclastic giant cells and low cellularity as the primary criteria associated with osteosarcomas. Positive expression of fibroblastlike cells, large amount of myxoid material and multinucleated cells were identified to be the key criteria for MFH. The analysis selected the presence of melanin as the major criterion for malignant melanomas, cells lying in lacunae for chondrosarcomas, fishhook nuclei for leiomyosarcomas, intracytoplasmic iron deposits for angiosarcomas and lipoblastlike cells for liposarcomas. CONCLUSION: From the previously described cytologic criteria, statistical analysis helped identify several key features that are significant in the evaluation of pleomorphic spindle cell neoplasms.

Biopsy, Needle↗
PubMed2003

A Cox regression analysis of covariates for asthma hospital readmissions.

BACKGROUND: Asthma hospital admissions and readmissions are unacceptably high, thus, a method to identify those at greatest risk could be helpful. METHODS: An observational retrospective study using a Cox regression to determine the relationship between the time interval between admissions and possible covariates of a readmission. The covariates were age, sex, ethnicity, smoking habit, history of allergy or eczema/hay fever, age of onset, Townsend index (TI), Jarman score (JS), and drugs on discharge. Those with p < 0.2, together with interacting covariates, from the preliminary analysis were eligible for the multivariate Cox regression analysis. RESULTS: Of the 523 patients admitted between 1994 and 1998 because of their asthma, complete data were available for 440. Of these, 112 were readmitted. Eligible covariates for the multivariate Cox regression analysis were sex, allergy status, history of eczema/hay fever, the JS and TI together with interactions between JS and TI, JS and allergy, and allergy with eczema/hay fever. There were 278 subjects (71 with a readmission) with complete data for these eligible covariates. The multivariate analysis revealed that female sex (odds ratio [OR] = 2.65, 95% confidence interval [CI] 1.42, 4.92), high JS (OR = 2.03, 95% CI 1.13-3.65), and history of allergy (OR = 1.88, 95% CI 1.06-3.32) formed the final model as significant predictors of readmission. CONCLUSION: Females with a history of allergy that were registered at a practice with a high workload (JS) had a higher risk of readmission. The analysis method used highlights how those at risk of readmission can be identified so that they can be targeted post discharge.

Adolescent↗
PubMed2002

Zero-inflated models for regression analysis of count data: a study of growth and development.

Poisson regression is widely used in medical studies, and can be extended to negative binomial regression to allow for heterogeneity. When there is an excess number of zero counts, a useful approach is to used a mixture model with a proportion P of subjects not at risk, and a proportion of 1--P at-risk subjects who take on outcome values following a Poisson or negative binomial distribution. Covariate effects can be incorporated into both components of the models. In child assessment, fine motor development is often measured by test items that involve a process of imitation and a process of fine motor exercise. One such developmental milestone is 'building a tower of cubes'. This study analyses the impact of foetal growth and postnatal somatic growth on this milestone, operationalized as the number of cubes and measured around the age of 22 months. It is shown that the two aspects of early growth may have different implications for imitation and fine motor dexterity. The usual approach of recording and analysing the milestone as a binary outcome, such as whether the child can build a tower of three cubes, may leave out important information.

Binomial Distribution↗
PubMed1992

A comparison of differential white cell counting on the Coulter VCS and the Technicon H1 using simple and multiple regression analysis.

This study uses the statistical methods of simple and multiple regression to compare the differential white blood count on the Coulter VCS and Technicon H1 analysers. The results demonstrate that both are good at distinguishing lymphocytes, neutrophils and eosinophils. Monocyte differential counts show disappointing correlation, both by simple and multiple regression techniques. Basophils, though less frequently a clinical problem, also correlated poorly in this study.

Basophils↗
PubMed1975

[Regression analysis of the relation between antitoxic activity of sera (Jensen method) and antibody titers in the passive hemagglutination reaction].

Antidiphtherial and antitetanus antitoxic immunity was determined in the sera of 1588 children (20 experiments) and 611 children and adults (12 experiments) by two methods--on animals and in the passive hemagglutination test (PHT). Factual data were grouped in accordance with a conditioned scale of the antitoxin values in IU composed of the values average for each interval. The series of two-fold dilutions represented a scale of titres of the same sera in the PHT. Mathematical analysis showed that there was a direct linear regressive relationship between the indices of antitoxic immunity obtained by different methods. As a rule, regression coefficients were below a unit, i. e. the rate of increase of the values by the HDT titre scale was somewhat retarded from the growth by the IU titre, this pointing to the difference in their value. The free member of the regression equation (a) characterizing this choice of the sera varied widely. Between the regression coefficients calculated for individual experiments statistically significant differences were revealed in almost 50% of cases. Transformation of quantitative indices of one test into quantitative characteristics obtained by the other method, with the aid of regression equation calculated outside the definite experiment, proved to be unfounded.

Adult↗
PubMed2003

[Multi-variate regression analysis of clinicopathological characteristics and prognosis of colorectal cancer].

OBJECTIVE: To evaluate the relationship between clinicopathologic features and prognosis of colorectal cancer after surgical treatment. METHODS: The clinical characteristics, pathologic features and survival rate of 761 patients with colorectal cancer after surgical treatment were univariately and multivariately analyzed. RESULTS: The overall 3- and 5-year survival rates of patients with colorectal cancer after surgical treatment were 62.9% and 60.7% with a median survival of 1,825 days. The factors of gross findings, degree of differentiation, infiltration, nodal and distant metastasis and neoplastic intestinal obstruction influenced the survival rate by univariate analysis. The factors of Dukes stage, gross tumor configuration, intramural spread and differentiation degree were available independent prognostic factors through multivariate analysis. CONCLUSION: Dukes stage, as the most important available independent prognostic factor (P < 0.0005), is able to assess the postoperative survival.

Adult↗
PubMed1999

Relationships between transcriptional and translational control of gene expression in Saccharomyces cerevisiae: a multiple regression analysis.

Natural selection for an increased translation efficiency has been proposed as the main determinant for the bias in codon usage observed in many genes of Saccharomyces cerevisiae. Recently, the efficiency of transcription of a large number of yeast genes has been determined, based on the cellular content of the respective mRNAs: this provides an additional dimension to the study of the multisep process of gene expression. Using a representative set of yeast genes with a known level of transcription, the relationship between transcriptional and translational steps was evaluated by a multiple linear regression model. This analysis demonstrated a positive correlation between the amount of transcript, given as the number of mRNA copies per cell for each individual gene, and indices evaluating the effects of translational selection on the corresponding codon usage pattern. This finding suggests a close association of the cellular mRNA content, regulated also at the transcriptional level, to its efficiency of translation, mediated by a fine-tuning of codon usage strategy. Moreover, multiple regression analysis demonstrated that the transcription level of a gene can be approximately predicted using indices of bias deriving from its nucleotide sequence. This allowed for an extensive investigation of uncharacterized regions of the complete genome sequence of S. cerevisiae, to detect new potential short protein coding genes that were not considered by previous searching procedures. Several small open reading frames exhibiting a statistically significant coding potential were thus identified as good candidates for functional analysis.

Amino Acid Sequence↗