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PubMed2005

Estimation of maturity of compost from food wastes and agro-residues by multiple regression analysis.

The composting process of food wastes and tree cuttings was examined on four composting types composed from two kinds of systems and added mixture of microorganisms. The time courses of 32 parameters in each composting type were observed. The efficient composting system was found to be the static aerated reactor system in comparison with the turning pile one. Using the multiple regression analysis of all the data (159 samples) obtained from this study, some parameters were selected to predict the germination index (GI) value, which was adopted as a marker of compost maturity. For example, using the regression model generated from pH, NH(4)(+) concentration, acid phosphatase activity, and esterase activity of water extracts of the compost, GI value was expressed by the multi-linear regression equation (p<0.0001). High correlations between the measured GI value and the predicted one were made in each type of compost. As a result of these observations, the compost maturity might be predicted by only sensing of the water extract at the composting site without any requirements for a large-size equipment and skill, and this prediction system could contribute to the production of a stable compost in wide-spread use for the recycling market.

Acid Phosphatase↗

PubMed1988

Neuroendocrine aspects of primary endogenous depression. VII. Logistic regression analysis of matched patient-control hormone data for discrimination between groups.

We previously reported significant alterations in hypothalamo-pituitary-adrenal cortical (HPA) and thyroid (HPT) axis function in a group of 40 primary, RDC definite endogenous depressives compared to 40 individually matched normal control subjects. In those reports, univariate statistical tests for matched samples were used (paired t-tests). We next wished to use both the HPA and the HPT measures in a multivariate analysis to discriminate the patients from the controls, but the paired nature of the hormone data obviated the use of standard techniques. With an adaptation of the BMDP PLR statistical program, we performed a matched logistic regression analysis, in stepwise fashion, which resulted in a model incorporating two HPA variables and one HPT variable. From this model, odds ratios which associate being depressed or not with levels of the HPA and HPT measures were estimated. The median odds ratio for the 40 matched pairs was 7.8. To illustrate the model, we present graphs of estimated odds ratios of patients with selected hormone values compared to a typical normal subject with hormone values close to the median values of the 40 controls in our study.

Adult↗

PubMed2005

Promotion to hospital consultant: regression analysis using NHS administrative data.

OBJECTIVES: To examine factors influencing promotion to hospital consultant. DESIGN: Multivariate logistic regression analysis of NHS administrative data between 1991 and 2000. SETTING: Hospitals in NHS Scotland. Population All registrars, senior registrars, and specialist registrars in Scotland. MAIN OUTCOME MEASURE: The proportion of doctors promoted to NHS consultant. RESULTS: Compared with doctors who graduated in Scotland, graduates from the rest of the United Kingdom and from overseas were less likely to be promoted to consultant (odds ratio 0.65, 95% confidence interval 0.52 to 0.82; and 0.37, 0.28 to 0.50, respectively). Promotion and holding an honorary contract before promotion were positively associated (1.37, 1.03 to 1.83); and the number of years since graduation (5.98 per year, 4.94 to 7.23). Women were less likely to be promoted (0.73, 0.60 to 0.90), as were doctors who worked part time (0.27, 0.17 to 0.42). Probabilities of promotion did not have a clear time trend between 1993 and 2000, and NHS boards in non-metropolitan areas of Scotland were more likely to offer promotions than NHS boards in metropolitan areas, presumably reflecting a higher gap between demand and supply in these boards. CONCLUSION: As the proportion of women in hospital medicine increases, government targets for the recruitment of consultants are unlikely to be met unless the promotion process is examined. It is unclear whether more recent reforms of the medical career structure will deal with these issues.

Career Mobility↗

PubMed1987

Evaluation of a Bayesian regression-analysis computer program using non-steady-state phenytoin concentrations.

The predictive performance of a Bayesian regression-analysis computer program that uses non-steady-state phenytoin data was evaluated. Forty patients receiving phenytoin or phenytoin sodium who had two or more non-steady-state serum concentrations were selected for study. Additional serum concentrations and dosing data were collected as they became available, but no effort was made to control the number or timing of serum concentration determinations. Patients were categorized into four groups for evaluation of the effect of potential bioavailability problems and length of dosing history (time over which serum concentration-time data were collected) on the ability to predict subsequent phenytoin concentrations. Population parameters for phenytoin maximum rate of elimination (Vmax), apparent Michaelis-Menten constant (Km), volume of distribution (V), and bioavailability (F) were obtained from the literature. Predictions based on serum phenytoin concentrations and dosing histories (information intervals) of 5 or 10 days were compared with predictions based on naive (population-based) estimates using prediction-error analysis. In each patient group, the use of either 5-day or 10-day information intervals resulted in a significant increase in precision and a significant reduction in bias compared with naive estimates. For the group of patients who initially had two or more serum concentrations within the first five days of monitoring, predictions showed a marked increase in bias and a decrease in precision as the time interval from the last measured concentration to the time of prediction increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Bayes Theorem↗

PubMed1997

Regression analysis of interval-censored survival data with covariates using log-linear models.

We considered the regression analysis of the event time data with left-, right-, or interval-censored observations. We extended life-table techniques for censored survival data using log-linear models to incorporate interval-censored failures. The EM algorithm was used to calculate maximum likelihood estimates for the parameters. We assumed that the hazard function was a stepwise function over disjoint intervals of time; thus, the nonparametric model, the parametric exponential model, and the semiparametric Cox proportional hazard model were easily implemented as special cases. We adapted the restricted EM algorithm to test hypotheses and to construct confidence intervals for the parameters. These methods were applied in an analysis of the recurrence time for treated melanoma patients.

Adult↗

PubMed1983

In vitro evaluation of Augmentin by broth microdilution and disk diffusion susceptibility testing: regression analysis, tentative interpretive criteria, and quality control limits.

Augmentin (Beecham Laboratories, Bristol, Tenn.), a combination drug consisting of two parts amoxicillin to one part clavulanic acid and a potent beta-lactamase inhibitor, was evaluated in vitro in comparison with ampicillin or amoxicillin or both for its inhibitory and bactericidal activities against selected clinical isolates. Regression analysis was performed and tentative disk diffusion susceptibility breakpoints were determined. A multicenter performance study of the disk diffusion test was conducted with three quality control organisms to determine tentative quality control limits. All methicillin-susceptible staphylococci and Haemophilus influenzae isolates were susceptible to Augmentin, although the minimal inhibitory concentrations for beta-lactamase-producing strains of both groups were, on the average, fourfold higher than those for enzyme-negative strains. Among the Enterobacteriaceae, Augmentin exhibited significantly greater activity than did ampicillin against Klebsiella pneumoniae, Citrobacter diversus, Proteus vulgaris, and about one-third of the Escherichia coli strains tested. Bactericidal activity usually occurred at the minimal inhibitory concentration. There was a slight inoculum concentration effect on the Augmentin minimal inhibitory concentrations. On the basis of regression and error rate-bounded analyses, the suggested interpretive disk diffusion susceptibility breakpoints for Augmentin are: susceptible, greater than or equal to 18 mm; resistant, less than or equal to 13 mm (gram-negative bacilli); and susceptible, greater than or equal to 20 mm (staphylococci and H. influenzae). The use of a beta-lactamase-producing organism, such as E. coli Beecham 1532, is recommended for quality assurance of Augmentin susceptibility testing.

Amoxicillin↗

PubMed1994

A SAS macro for residual deviance of ordinal regression analysis.

In this paper, a SAS macro is described for calculating the likelihood of the 'saturated' model in the analysis of ordinal regression. The outcome variable is multinomial on an ordinal scale, while the explanatory variables can be nominal or ordinal. Several ordinal regression models may be fitted to the data. One method of testing for the goodness of fit of these regression models is by comparing the residual deviance with the chi 2 distribution. In SAS, PROC LOGISTIC may be used to fit this type of data with proportional odds model. Unfortunately, the residual deviance is not available from the output. Our SAS macro will supplement the SAS output so that the residual deviance test may be carried out. The data from an ongoing HIV study is used as an illustration.

Bias↗

PubMed1996

Sonography of pregnancies with first-trimester bleeding and a viable embryo: a study of prognostic indicators by logistic regression analysis.

The objective of our study was to investigate the relationship between sonographic findings and the occurrence of abortion in pregnancies complicated by first-trimester bleeding in which fetal cardiac activity was documented upon admission. A prospective study of transvaginal sonography was performed in 270 pregnant patients with bleeding between 5 and 12 weeks' gestation. The study group included 149 cases in which a singleton fetus with cardiac activity was initially documented. The outcome variable was pregnancy loss prior to 20 weeks. The influence of sonographic findings on admission was studied by univariate analysis and logistic regression. The prevalence of abortion was 23/149 (15%). A significant relationship (p < 0.05) was found between the occurrence of abortion and the following: fetal bradycardia (heart rate less than -1.2 SD from the mean), a discrepancy between the diameter of the gestational sac and crown-rump length less than -0.5 SD from the mean, and a discrepancy between menstrual and sonographic age of more than 1 week. According to the logistic regression equation that was obtained, the probability of abortion in first-trimester bleeding with documented fetal cardiac activity upon admission varied between a minimum of 6% when none of the above risk factors were present and a maximum of 84% when all were present. The presence of any of the above factors identified 84% of all subsequent abortions.

Abortion, Spontaneous↗

PubMed1990

[Conditional logistic regression analysis and path analysis of risk factors of cervical cancer].

A case-control study of 125 pairs was carried out in Jinan during 1987-1988. 39 variables were analysed with the single factor analysis, 14 factors were confirmed as the suspicious risk factors. Conditional Logistic regression analysis of the above 14 factors was used. Results showed that the following five risk factors were associated with cervical cancer, i.e., cervical erosion, low family income, poor personal hygiene during menstrual period, sexual factors and early age at marriage. The causal model with 9 risk factors of cervical cancer was set up and studied with path analysis. The result indicated that 4 risk factors had direct and indirect influence on the occurrence of cervical cancer respectively.

Carcinoma, Squamous Cell↗

PubMed1993

[An application of multiple logistic regression analysis to an outcome study on surgery for patients with femoral neck fracture].

Sixty five patients with femoral neck fracture were examined to find any risk factor for their postoperative complications. Here, postoperative complications included cardiac catastrophe, pulmonary embolism, central nervous system accident, and respiratory failure requiring mechanical ventilation during the period of one week after operation. Multiple logistic regression analysis was used to predict these factors. Explanatory variables were selected based on the clinical judgement. Those variable are age, sex, preoperative underlying cardiac disease, preoperative underlying respiratory complications, the use of cement for the procedure, and anesthetic technique. The analysis revealed that the sex was the only variable that was considered significant based on the P value less than 0.05. However, multi-colinearity between variables was suspected to exist based on the correlation matrix analysis which may indicate that the factor is not, in fact, significant. In short, further study will be required to find any significant variables or risk factors to predict the outcome of untoward events.

Aged↗

PubMed1993

[From multiple regression analysis to logistic model, proportional hazard model and log linear model. Its concept and application].

Recently logistic model, proportional hazard model and log linear model have been used frequently in the medical literatures. Here, each model is reviewed briefly from basics to its application, pointing out pitfalls in its application, some of which are common to any regression analysis. The logistic model is especially useful for the analysis of retrospective data where odds ratio is utilized to evaluate the outcome probability. On the other hand, proportional hazard model is useful when we analyze censored data, utilizing hazard function. Log linear model has been used where contingency table has more than three independent variables, the situation where its applicability in clinical medicine is wide. Familiarity with these statistical methods would enable us to evaluate data more effectively and efficiently and ultimately to read literature more easily.

Models, Statistical↗

PubMedDate not supplied

Factors predictive of heightened third-day bilirubin levels: a multiple stepwise regression analysis.

The purpose of this research was to prospectively study the variables contributing to the variance in third-day bilirubin levels in healthy, full-term newborns. The study subjects were 252 full-term, healthy infants born at the University of Kansas Medical Center over a four-month period. Using a multiple stepwise regression analysis, six factors were found to be significant predictors of higher third-day bilirubin levels: higher cord bilirubin level; lower total serum protein in the infant on admission to the nursery; sex of the child; administration of promethazine hydrochloride during labor; greater weight loss in the infant; and breast-feeding. Several other factors which have been implicated previously--including use of oxytocin for induction or augmentation of labor, previous use of birth control pills by the mother, prolonged rupture of membranes prior to delivery, type of delivery, race, and epidural anesthesia--were not found to be significant predictors of third-day bilirubin levels once the six variables listed had been taken into consideration. The results are discussed in terms of past research as well as implications for clinical practice.

Bilirubin↗

PubMed2002

Detection of pleiotropic effects of quantitative trait loci in outbred populations using regression analysis.

In this paper a method is presented to determine pleiotropic quantitative trait loci (QTL) or closely linked QTL in an outbred population. The method is based on results from single-trait analyses for different traits and is derived for a granddaughter design. The covariance between estimated contrasts of grandsires obtained in single-trait regression analysis is computed. When there is no pleiotropic QTL, the covariance between contrasts depends on the heritabilities of the traits involved, the polygenic and environmental correlation between the traits, the phenotypic standard deviations, the number of sires per grandsire, and the number of daughters per sire. A pleiotropic QTL results in a covariance that deviates from this expected covariance. The deviation depends on the size of the effects on both traits and on the fraction of grandsires heterozygous for the QTL. When analyzing experimental data, the expected covariance and the confidence interval for the expected covariance can be determined by permutation of the data. A covariance outside the confidence interval suggests the presence of a pleiotropic QTL or a closely linked QTL. The method is verified by simulation and illustrated by analyzing an experimental data set on chromosome 6 in dairy cattle.

Animals↗

PubMed2003

The effect of childhood maltreatment on adult criminality: a tobit regression analysis.

This article reports on the results of an analysis of a data set containing information on 667 nonmaltreated and 908 maltreated children. The data also contain information on whether the study subjects were arrested in early adulthood. Because adult arrests are an imperfect and censored measure of antisocial behavior, tobit regression analysis was used to examine the effect of the subjects' experiences of child maltreatment on later arrests while controlling for those subjects' demographic characteristics. The analysis finds that children's age, race, and sex and experiences of child neglect all have an impact on subsequent adult arrests. However, physical abuse and sexual abuse do not emerge as statistically significant predictors of arrests in this model. The study also illustrates a method for the decomposition of tobit coefficients to extract more information from them.

Adult↗

PubMed1994

Prognosis of first-trimester twin pregnancies: polychotomous logistic regression analysis.

PURPOSE: To determine which clinical and sonographic characteristics independently affect the prognosis of first-trimester twin pregnancies and to develop formulas for calculating the probabilities of the pregnancy resulting in two, one, or no liveborn infants. MATERIALS AND METHODS: The authors prospectively identified 137 twin pregnancies with two heartbeats at first-trimester sonography and with known pregnancy outcome. Stepwise polychotomous logistic regression analysis was used to identify characteristics that have an independent statistically significant relationship with pregnancy outcome and to develop outcome-prediction formulas. RESULTS: Of 137 patients, 110 (80.3%) had viable twins, 12 (8.8%) had one infant, and 15 (10.9%) had none. Gestational age, chorionicity, and sonographic findings were independent, statistically significant (P < .05) prognostic factors, while maternal age, method of conception, and indication for sonography were not. CONCLUSION: The logistic regression formulas involving the three independent prognostic factors can be used in the first trimester to predict pregnancy outcome.

Adult↗

PubMed1990

Prediction of mortality by logistic regression analysis in patients with postoperative enterocutaneous fistulae.

The contrasting results of treatment of patients with postoperative enterocutaneous fistulae reflect the heterogeneity of the disease and depend on the patient's condition and the characteristics of the fistulae. For this reason, the use of a prognostic index, which enables such patients to be classified according to their risk of death, could be useful. In this study we propose a prognostic index based on a logistic regression analysis, obtained by using two (APACHE II score and serum albumin concentration) of the eight risk factors that have been retrospectively analysed in a series of 70 patients with postoperative enterocutaneous fistulae treated in our surgical department since 1981. The logistic regression equation indicates that patients with a probability of dying of less than 0.35 have a good prognosis, with a sensitivity of 90 per cent, a specificity of 90 per cent, a negative predictive value of 79 per cent, a positive predictive value of 96 per cent and an accuracy of 90 per cent. The predictive performance of the index has also been evaluated in a group of 17 patients studied prospectively, and this confirms the sensitivity and specificity of the model. This postoperative enterocutaneous fistulae index could be a helpful tool in clinical trials and surgical audit.

Adult↗

PubMed1987

Age and duration of illness as predictors of ventricular brain ratio (VBR) size in chronic schizophrenic patients. A stepwise regression analysis study.

The CT scans of 18 chronic schizophrenic patients and 17 controls were evaluated for Ventricular Brain Ratio (VBR) size. A trend for the patient group to have larger VBR than controls was present but did not reach statistical significance at the 5% level. Age was found to be an important correlate of VBR within the patient group but not among controls. In a stepwise multiple-regression model age, among other independent variables, can account for 47% of VBR variance in schizophrenic patients. Linear regression analysis did not reveal significant association between VBR and age in control subjects.

Adult↗

PubMed2006

Fractal dimension in human cortical surface: multiple regression analysis with cortical thickness, sulcal depth, and folding area.

Fractal dimension (FD) has been widely used to provide a quantitative description of structural complexity in the cerebral cortex. FD is an extremely compact measure of shape complexity, condensing all details into a single numeric value. We interpreted the variation of the FD in the cortical surface of normal controls through multiple regression analysis with cortical thickness, sulcal depth, and folding area related to cortical complexity. We used a cortical surface showing a reliable representation of folded gyri and manually parcellated it into frontal, parietal, temporal, and occipital regions for regional analysis. In both hemispheres the mean cortical thickness and folding area showed significant combination effects on cortical complexity and accounted for about 50% of its variance. The folding area was significant in accounting for the FD of the cortical surface, with positive coefficients in both hemispheres and several lobe regions, while sulcal depth was significant only in the left temporal region. The results may suggest that human cortex develops a complex structure through the thinning of cortical thickness and by increasing the frequency of folds and the convolution of gyral shape rather than by deepening sulcal regions. Through correlation analysis of FD with IQ and the number of years of education, the results showed that a complex shape of the cortical surface has a significant relationship with intelligence and education. Our findings may indicate the structural characteristics that are revealed in the cerebral cortex when the FD in human brain is increased, and provide important information about brain development.

Adult↗