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PubMed1985

Multiple logistic function versus Mantel-Haenszel procedure in the analysis of risk factors for prevalence of hepatitis A antibodies.

Multiple logistic function and Mantel-Haenszel procedure are compared in their ability to control confounding in a large set of data. In this specific application substantial equivalence is found between the two techniques. When both techniques are applicable and data are not sparse, the authors prefer stratification, which is simpler and free of assumptions.

Hepatitis A↗

PubMed1990

Global behaviour of age-dependent logistic population models.

We study the large time behaviour of a nonlinear population model with a general logistic term. It is proved that every solution must have a limit when time becomes infinite. We present conditions that guarantee the boundedness of the solution. Furthermore, we prove that in general no oscillation is possible for the total number of population. This is in sharp contrast to the linear case.

Aging↗

PubMed1982

On the global stability of the logistic age-dependent population growth.

We study an age-dependent population equation with a nonlinear death rate of "logistic" type. The global asymptotic stability of the null solution is investigated when R(0) less than 1. If R(0) greater than 1 we get the existence of a nontrivial steady state that becomes asymptotically stable itself, while the null solution is unstable. The rate of decay is estimated.

Aging↗

PubMed1986

Optimal harvesting of a logistic population in an environment with stochastic jumps.

Dynamic programming is employed to examine the effects of large, sudden changes in population size on the optimal harvest strategy of an exploited resource population. These changes are either adverse or favorable and are assumed to occur at times of events of a Poisson process. The amplitude of these jumps is assumed to be density independent. In between the jumps the population is assumed to grow logistically. The Bellman equation for the optimal discounted present value is solved numerically and the optimal feedback control computed for the random jump model. The results are compared to the corresponding results for the quasi-deterministic approximation. In addition, the sensitivity of the results to the discount rate, the total jump rate and the quadratic cost factor is investigated. The optimal results are most strongly sensitive to the rate of stochastic jumps and to the quadratic cost factor to a lesser extent when the deterministic bioeconomic parameters are taken from aggregate antarctic pelagic whaling data.

Animals↗

PubMed1984

Clinical macrovascular disease in Caucasoid diabetic subjects: logistic regression analysis of risk variables.

A cross-sectional study of 1084 Caucasoid diabetic subjects in rural Western Australia revealed a high rate of clinical macrovascular disease (46%), including coronary heart disease (13%), stroke (8%), and peripheral vascular disease (38%). Age was the major time-related variable for total macrovascular disease and for peripheral vascular disease, with identical prevalence rates in Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes when age was taken into account. In 179 Type 1 diabetic subjects, logistic regression analysis showed no associated risk factors other than age. In 905 Type 2 diabetic subjects the independent risk factors for total macrovascular disease, identified by a forward step-wise selection procedure, were age as the major contributor, with plasma creatinine levels and plasma glucose levels (all p less than 0.001), high-density lipoprotein cholesterol levels, serum total cholesterol levels, and the (supine-erect) systolic blood pressure difference (all p less than 0.05). There were no direct associations with percentage desirable weight, cigarette smoking or male sex. Type 2 diabetic subjects demonstrated a very strong negative association between high-density lipoprotein cholesterol levels and coronary heart disease, and significant associations were found also between plasma glucose levels and coronary heart disease (p less than 0.01), and glycosylated haemoglobin levels and peripheral vascular disease (p less than 0.001).

Adolescent↗

PubMed1986

Hospital characteristics and the use of computer processing and abstract services. A logistic analysis.

The use of computer processing and abstract services by hospitals is in a state of continuing change. Although many hospitals subscribe to abstract or turnkey systems, others are leaving shared services to set up their own in-house systems. To better understand the relationship between hospital characteristics and the use of computer processing and/or abstract services, data from the AHA 1982 Special Survey on Selected Hospital topic were analyzed using logistic regression analysis. Hospital size, ownership, and region were clearly related to the use of computer processing and/or abstract services for processing discharge data. Teaching status was also related to the use of abstract services, although teaching status hospitals also reported more reliance on in-house computer processing. Hospitals located in SMSAs and belonging to chains reported a higher use of discharge abstract services, and hospitals with higher operating margins were more likely to use abstract services on an "off-line" or batch-processing basis. The significance of these findings and their implications for abstract services are discussed.

Abstracting and Indexing↗

PubMed1982

Comparing two head injury treatments by linear logistic model.

A linear logistic model is used to compare the performance of a series of head injured patients treated in Auckland with a series obtained from the International Data Bank (IDB), on head injured patients. The IDB patients were treated along conventional lines of neurosurgical management. The Auckland patients were submitted to a regime of elective artificial ventilation of the lungs and heavy sedation, directed against diffuse brain swelling. Two types of comparison were used. First, a model was constructed from the Auckland data of the relationship of outcome to factors relating to the severity of the head injury. This input-output relationship was used to predict the distributions of outcome in the IDB series. Secondly, a descriptive model on the combined Auckland and IDB data was given the option of selecting a dummy variable to indicate whether the source of the patient, Auckland or IDB, had significantly influenced outcome for a given set of other determinants. Differences between Auckland and IDB were only significant if the severity of the head injury in the IDB cases was represented by the set of scores indicating their best condition over the first 24 hours of coma. The scores indicating the condition of the Auckland patients might be comparable to either the 24 hour best or the 24 hour worst IDB scores. One cannot say whether any differences in input-output relationships between the two series arise from differences in coding the input data or from real differences in outcome for given sets of determinants of outcome.

Adolescent↗

PubMed2003

[Evaluation of potential liver living donors. Logistic and financial aspects].

INTRODUCTION: The increasing shortage of cadaveric organs makes living-related liver transplantation a more and more important option. Safety for the donor has the highest priority, and therefore detailed and thorough evaluation is needed. MATERIALS AND METHODS: All potential donors who had been evaluated at our center from January 2001 to March 2002 ( n=100) were included in a retrospective study to analyse the qualitative, logistical, and economic aspects of the evaluation. RESULTS: Seventy-three percent of the potential donors were found to be unsuitable for living donation during the evaluation process. The main reasons were: uncompatible blood group, availability of cadaveric transplant by Eurotransplant, steatosis of more than 10% of hepatocytes in liver biopsy, insufficient liver volume, and psychosocial reasons. The expenditure for all scheduled investigations was 4,469 euro for a complete evaluation. CONCLUSION: While on the one hand, high standards of the evaluation process must be guaranteed, insufficient reimbursement on the other should not lead centers to reduce either quantity or quality of necessary examinations entered in the evaluation protocol.

Adult↗

PubMed2002

[Interdisciplinary shock room management: personnel, equipment and spatial logistics in 3 trauma centers in Europe].

OBJECTIVE: To analyse common and divergent features of staff-related, equipmental and spatial/logistical concepts of three large trauma centers of highest health care level. METHODS: The health care mandate as well as the staff management, the organisational and the constructional-spacial structure of trauma room diagnostics and therapy of the trauma centers of the Universities of Leiden and Munich (Innenstadt) and the Zentralklinikum Augsberg are described. In particular the technical equipment and the process of the radiological diagnostic procedures in the trauma room are outlined. RESULTS: Staff availability and basic technical equipment of the trauma rooms are comparable between the three hospitals. Divergent concepts exist concerning the complexity of the initial radiologic examination protocols. Spacial connection and importance of computed tomography are also discussed controversially. Urgent interventional procedures are increasingly performed within the trauma room. Magnetic-resonance-tomography does not play a role in early care from multiple injured patients. CONCLUSION: Trauma centers have to meet certain personnel and technical prerequisites to guarantee a temporally optimised care for multiple injured patients. Differences between the three centers concerning the logistic sequence and the radiologic examination techniques used are mainly due to variable emphasis put on CT in the initial phase of patient care.

Critical Care↗

PubMed1999

Bacterial growth in space flight: logistic growth curve parameters for Escherichia coli and Bacillus subtilis.

Previous investigations have reported that bacterial suspension cultures grow to higher stationary concentrations in space flight than on Earth; however, none of these investigations included extensive ground controls under varied inertial conditions. This study includes extensive controls and cell-growth data taken at several times during lag phase, log phase, and stationary phase of Escherichia coli and Bacillus subtilis. The Marquardt-Levenberg, least-squares fitting algorithm was used to calculate kinetic growth parameters from the logistic bacterial growth equations for space-flight and control growth curves. Space-flight cultures grew to higher stationary-phase concentrations and had shorter lag-phase durations. Also, evidence was found for increased exponential growth rate in space.

Bacillus subtilis↗

PubMed2003

Trail impacts in Sagarmatha (Mt. Everest) National Park, Nepal: a logistic regression analysis.

A trail study was conducted in the Sagarmatha (Mt. Everest) National Park, Nepal, during 1997-1998. Based on that study, this paper examines the spatial variability of trail conditions and analyzes factors that influence trail conditions. Logistic regression (multinomial logit model) is applied to examine the influence of use and environmental factors on trail conditions. The assessment of trail conditions is based on a four-class rating system: (class I, very little damaged; class II, moderately damaged, class III, heavily damaged; and class IV, severely damaged). Wald statistics and a model classification table have been used for data interpretation. Results indicate that altitude, trail gradient, hazard potential, and vegetation type are positively associated with trail condition. Trails are more degraded at higher altitude, on steep gradients, in areas with natural hazard potential, and within shrub/grassland zones. Strong correlations between high levels of trail degradation and higher frequencies of visitors and lodges were found. A detailed analysis of environmental and use factors could provide valuable information to park managers in their decisions about trail design, layout and maintenance, and efficient and effective visitor management strategies. Comparable studies on high alpine environments are needed to predict precisely the effects of topographic and climatic extremes. More refined approaches and experimental methods are necessary to control the effects of environmental factors.

Climate↗

PubMed1985

A logistic regression analysis of multiple noninvasive tests for the prediction of the presence and extent of coronary artery disease in men.

The incremental diagnostic yield of clinical data, exercise ECG, stress thallium scintigraphy, and cardiac fluoroscopy to predict coronary and multivessel disease was assessed in 171 symptomatic men by means of multiple logistic regression analyses. When clinical variables alone were analyzed, chest pain type and age were predictive of coronary disease, whereas chest pain type, age, a family history of premature coronary disease before age 55 years, and abnormal ST-T wave changes on the rest ECG were predictive of multivessel disease. The percentage of patients correctly classified by cardiac fluoroscopy (presence or absence of coronary artery calcification), exercise ECG, and thallium scintigraphy was 9%, 25%, and 50%, respectively, greater than for clinical variables, when the presence or absence of coronary disease was the outcome, and 13%, 25%, and 29%, respectively, when multivessel disease was studied; 5% of patients were misclassified. When the 37 clinical and noninvasive test variables were analyzed jointly, the most significant variable predictive of coronary disease was an abnormal thallium scan and for multivessel disease, the amount of exercise performed. The data from this study provide a quantitative model and confirm previous reports that optimal diagnostic efficacy is obtained when noninvasive tests are ordered sequentially. In symptomatic men, cardiac fluoroscopy is a relatively ineffective test when compared to exercise ECG and thallium scintigraphy.

Adult↗

PubMed1983

Logistic models for prediction of enteric morbidity in the treatment of ovarian and cervical cancers.

To identify patients at high risk for the development of enteric injury, an analysis was made of 212 women who received extensive pelvic and abdominal radiotherapy at the University of Minnesota from 1970 through 1981. One hundred one patients with cervical carcinomas received 8,000 to 8,500 rads to point A, 6,000 rads to point B, and 4,500 to 5,075 rads to the periaortic lymph nodes. One hundred eleven women with ovarian cancers received 2,000 rads to the entire abdomen, followed by an additional 2,975 to 3,000 rads to the pelvis. The overall complication rate was 6.6% (14/212). The only patients who sustained chronic radiation morbidity had thin physiques. The maximum likelihood multiple logistic model was utilized to predict the probability of enteric injury as a function of thin physique, previous operations, and hypertension for individual patients. The usefulness of predictive models is discussed, and possible reasons for the susceptibility of thin women to ionizing radiation are explored.

Adolescent↗

PubMed1978

A computer program for stepwise logistic regression using maximum likelihood estimation.

A computer program has been written which performs a stepwise selection of variables for logistic regression using maximum likelihood estimation. The selection procedure is based on likelihood ratio tests for the coefficients. These tests are used in a forward selection and a backward elimination at each step. The use of the program is illustrated by several examples.

Computers↗

PubMed1985

A program for logistic prediction modelling.

A computer program has been developed that can be used for analysing a binary outcome variable and a set of regressors of type interval with a logistic (i.e. nonlinear) model.

Biometry↗

PubMed1985

Critical evaluation of quadratic logistic discriminant analysis methods: a case study.

Electrocardiographic measurements from two groups, patients with left ventricular hypertrophy and clinically normal cases, were analyzed to illustrate the performance of the linear logistic discrimination method in the case of very unequal covariance matrices. Two quadratic extensions of the linear model were critically investigated. The use of graphical methods to check the model has been stressed and illustrated.

Biometry↗

PubMed1985

The use of a logistic model for the quantitative interpretation of indirect sandwich enzyme labelled immunosorbent assays (ELISA) for antibodies and antigens in foot and mouth disease.

A three parameter logistic model is described for the analysis of profiles of optical density vs log dose for indirect sandwich ELISA tests in foot and mouth disease. The model describes the observed phenomenon of saturability with increasing dose, and its parameters can be interpreted in terms of molecular binding events. A computer program to fit the model is described. An approximate statistical test is developed which can be used to test for departures from equivalence for replicate profiles. It is found that correlation of the optical density values to a standard reference reaction considerably improves reproducibility.

Animals↗

PubMed1987

Calculation of odds ratios on the TI-59 from logistic regression output.

A program for the Texas Instruments TI-59 and, optionally, a print cradle is described that allows calculation of point estimates and confidence intervals for odds ratios using information included in the output from most logistic regression programs. The program considers up to fifteen continuous and/or dichotomous independent variables.

Biometry↗