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PubMed1986

Risk assessment for case-control subgroups by polychotomous logistic regression.

Case-control studies involving more than two disease and referent categories may be analyzed by means of polychotomous logistic regression, an extension of the usual dichotomous logistic regression model. Although the standard method still may be used to compare the several disease subgroups in pairs, the polychotomous approach is advantageous in that it allows simultaneous estimation of the disease-specific parameters and direct hypothesis testing involving multiple disease categories. This is especially useful for assessing whether different disease types have different risk factors. The method is applied to a large case-control study of breast cancer involving three disease categories for which both categoric and continuous risk factors are considered. Substantive epidemiologic interpretation of polychotomous regression outputs is emphasized, as well as providing illustration of the practical aspects of the statistical method.

Adult↗

PubMed1986

A program for logistic regression on the IBM PC.

Logistic regression is one of the most frequently used tools of epidemiologic analyses. This paper describes a program to accomplish interactive logistic analysis on the IBM PC and compatibles by using the disk operating system. The program provides most statistics of interest to epidemiologists, including confidence intervals for estimated coefficients and estimated odds ratios.

Computers↗

PubMed1996

Early diagnosis of acute myocardial infarction using clinical and electrocardiographic data at presentation: derivation and evaluation of logistic regression models.

The aim of this study was to determine which, and how many, data items are required to construct a decision support algorithm for early diagnosis of acute myocardial infarction using clinical and electrocardiographic data available at presentation. Logistic regression models were derived using data items from 600 consecutive patients at one centre (Edinburgh), then tested prospectively on 510 cases from the same centre and 662 consecutive cases from another centre (Sheffield). Although performance of the models increased with progressive addition of data inputs when applied to training data, a simple six-factor model was the most effective on test data, yielding accuracies of 84.3 and 83.6% on the two test sets. A model constructed solely of electrocardiographic data performed nearly as well as those incorporating clinical data. Previously published logistic regression models did not perform so well as the models derived from data collected for this study.

Adolescent↗

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↗

PubMed2006

New disseminated intravascular coagulation score: A useful tool to predict mortality in comparison with Acute Physiology and Chronic Health Evaluation II and Logistic Organ Dysfunction scores.

OBJECTIVE: To compare the performance of a coagulation score-the new scoring system for diagnosing disseminated intravascular coagulation (DIC)-with the Acute Physiology and Chronic Health Evaluation (APACHE) II and Logistic Organ Dysfunction score in mortality prediction. DESIGN: Single-center retrospective study. SETTING: Medical intensive care unit of the University of Munich. PATIENTS: A total of 797 patients admitted to the intensive care unit between January 1, 1996, and January 1, 2001. METHODS: A retrospective analysis of all patients was done if the coagulation variables d-dimer, platelet count, fibrinogen, and prothrombin index were available within the first 12 hrs after admission. Patients with missing values, fibrinolytic therapy, or unknown survival status were excluded from analysis. As a marker of fibrin generation, d-dimer was measured and integrated into the scoring system for DIC together with prothrombin time, fibrinogen, and platelet count. A coagulation score was calculated in analogy with the scoring system for DIC in patients not typically developing DIC. MEASUREMENTS AND RESULTS: Overall, the mean result of the scoring system for DIC was 2.2 points. An increasing scoring system for DIC was associated with increasing mortality in patients with serious infections. Use of the scoring system for DIC in addition to the APACHE II score helps to predict mortality better than the APACHE II score alone, especially in patients with infections. The Cox regression analysis showed that the DIC and APACHE II scores correlated independently with survival time with a greater effect of the DIC score than the APACHE II or the Logistic Organ Dysfunction score. Similar results were obtained using the coagulation score in patients with cardiocirculatory diseases. CONCLUSION: Our retrospective data suggest that a combination of the APACHE II score and the scoring system for DIC predicts mortality in critically ill patients with available variables better than the APACHE II score alone. This effect is most pronounced among patients with active infection. These results of our retrospective analysis have to be confirmed in a prospective study.

APACHE↗

PubMed2001

Delayed coupling of logistic maps.

We study the synchronization of logistic maps in a one-way coupling configuration. The master system is coupled to the slave system with a delay n(1), and the slave is a delayed logistic map with a delay n(2). We show that when the slave system has no delay (n(2)=0), perfectly synchronized solutions exist for strong enough coupling. In these solutions the slave variable y is retarded with respect to the master variable x with a retardation equal to the delay of the coupling [y(i+n(1))=x(i)]. When n(2) not equal 0, a regime of generalized synchronization is observed, where y(i+n(1)) is synchronized with x(i), but not completely, since the master and the slave systems obey different maps. We introduced a similarity function as an indicator of the degree of synchronization and, using a noisy master source, distinguished synchronization from noise-induced correlations.

Journal Article↗

PubMed2006

Nonlocal competition and logistic growth: patterns, defects, and fronts.

Logistic growth of diffusing reactants on spatial domains with long-range competition is studied. The bifurcations cascade involved in the transition from the homogeneous state to a spatially modulated stable solution is presented, and a distinction is made between a modulated phase, dominated by single or few wave numbers, and the spiky phase, where localized colonies are separated by depleted region. The characteristic defects in the periodic structure are presented for each phase, together with the invasion dynamics in the case of local initiation. It is shown that the basic length scale that controls the bifurcation is the width of the Fisher front, and that the total population grows as this width decreases. A mix of analytic results and extensive numerical simulations yields a comprehensive examination of the possible phases for logistic growth in the presence of nonlocal competition.

Journal Article↗

PubMed2005

Sparse multinomial logistic regression: fast algorithms and generalization bounds.

Recently developed methods for learning sparse classifiers are among the state-of-the-art in supervised learning. These methods learn classifiers that incorporate weighted sums of basis functions with sparsity-promoting priors encouraging the weight estimates to be either significantly large or exactly zero. From a learning-theoretic perspective, these methods control the capacity of the learned classifier by minimizing the number of basis functions used, resulting in better generalization. This paper presents three contributions related to learning sparse classifiers. First, we introduce a true multiclass formulation based on multinomial logistic regression. Second, by combining a bound optimization approach with a component-wise update procedure, we derive fast exact algorithms for learning sparse multiclass classifiers that scale favorably in both the number of training samples and the feature dimensionality, making them applicable even to large data sets in high-dimensional feature spaces. To the best of our knowledge, these are the first algorithms to perform exact multinomial logistic regression with a sparsity-promoting prior. Third, we show how nontrivial generalization bounds can be derived for our classifier in the binary case. Experimental results on standard benchmark data sets attest to the accuracy, sparsity, and efficiency of the proposed methods.

Algorithms↗

PubMed2000

Using conditional logistic regression to fit proportional odds models to interval censored data.

An easily implemented approach to fitting the proportional odds regression model to interval-censored data is presented. The approach is based on using conditional logistic regression routines in standard statistical packages. Using conditional logistic regression allows the practitioner to sidestep complications that attend estimation of the baseline odds ratio function. The approach is applicable both for interval-censored data in settings in which examinations continue regardless of whether the event of interest has occurred and for current status data. The methodology is illustrated through an application to data from an AIDS study of the effect of treatment with ZDV+ddC versus ZDV alone on 50% drop in CD4 cell count from baseline level. Simulations are presented to assess the accuracy of the procedure.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Growth in solid heterogeneous human colon adenocarcinomas: comparison of simple logistical models.

Three models of simple logistical growth were used to describe volumetric growth in heterogeneous tumours. Two clonal subpopulations (designated as clone A and clone D) originally obtained from a human colon adenocarcinoma were used to produce solid xenograft tumours in nude mice. Volumetric growth of tumours produced from pure cells alone was compared to that produced from 50% A:50% D, 88% A:12% D, and 9% A:91% D admixtures. Gompertzian analysis of the in vivo growth data indicated significant differences in both the initial growth rates and final asymptotic limiting volumes of the pure versus the admixed tumours. Verhulstian and modified Verhulstian models were also used to derive regression curves from the same data. The fit of the curves was compared with each other using standard (Akaike, 1974; Schwartz, 1978) information criteria. In four of the five tumour populations the Gompertz equation fitted best. Only in the 88% A:12% D tumours did the modified Verhulst model fit best. The deviations from the regression curves, the residuals, for all three models were systematically distributed. These systematic errors are likely to be the result of using simplified logistical models to describe the growth kinetics of interacting populations in heterogeneous tumours.

Adenocarcinoma↗

PubMed2004

Incidental carcinoma of the prostate: clinicopathological, stereological and immunohistochemical findings studied with logistic regression and self-organizing feature maps.

OBJECTIVE: To identify significant predictive factors determining category T1a and T1b in incidental prostatic carcinoma with classical and neural multivariate data analysis methods. MATERIALS AND METHODS: Incidental prostatic carcinomas diagnosed in our department during 1990-99 (66 cases) were re-examined. Besides acquiring routine clinical and pathological data the tumours were assessed by scoring immunohistochemistry for proliferative activity and p53-overexpression. Tumour vascularization (angiogenesis) and epithelial texture variables were investigated by quantitative stereology. The data were evaluated by classical statistical methods (t-test, correlation analysis, logistic regression). Moreover, self-organizing feature maps (SOMs) were applied as an exploratory approach to unsupervised data analysis by artificial neural networks. RESULTS: The proliferative fraction, p53 overexpression of tumour cell nuclei, preoperative prostate-specific antigen value and density of capillary vascularization correlated with the Gleason score in incidental prostatic carcinoma. In a stepwise logistic regression analysis with the tumour categories T1a and T1b as dependent variables, the Gleason score and the volume fraction of epithelial cells were significant independent predictors of the tumour category. The cases could be grouped into clusters of different degrees of malignancy using SOMs. CONCLUSIONS: Texture variables of tumour cells are of central importance for the extent of propagation in the prostate in incidental prostatic adenocarcinomas. Gleason score and quantitative stereological estimates of the volume fraction of tumour cells are significant predictors of T1a and T1b categories of incidental prostatic carcinoma. Unsupervised clustering of T1 prostate carcinoma cases by SOMs correlates well with the dichotomous classification into T1a and T1b according to the UICC.

Aged↗

PubMed1994

Immunohistochemical reactivity in mesothelioma and adenocarcinoma: a stepwise logistic regression analysis.

Histological sections from 103 malignant mesotheliomas and 43 adenocarcinoma metastases in pleural biopsies were investigated for reactivity against a panel of 11 different antibodies. The size of the material allowed the evaluation by stepwise logistic regression analysis, which selected five parameters of major importance: vimentin reactivity in epithelial cells, reactivity to low-molecular-weight keratins in fibrous cells, strong membrane accentuation of EMA reactivity, and lack of reactivity to LeuM1 and BerEp4. Three of these criteria were sufficient to identify a mesothelioma with high specificity and with a sensitivity of approximately 70%. Whilst the monoclonal anti-CEA tested was the most valuable single parameter, it did not add any diagnostic information to the combination of criteria selected by the stepwise logistic regression analysis. However, this antibody can be used to exclude most of the adenocarcinomas from further analysis with the more extensive panel.

Adenocarcinoma↗

PubMed1996

Identifying environmental risk to male reproductive function by occupational sperm studies: logistics and design options.

Malfunction of the male reproductive system might be a sensitive marker of environmental hazards, the effects of which may extend beyond reproductive function. The testis is more vulnerable to heat and ionising radiation than any other organ of the body and several xenobiotics are known to disrupt spermatogenesis after low level exposure. Studies of environmental impact on human health are often most informative and accurate when carried out in the workplace where exposures can be high and easy to document. Semen analysis provides readily obtainable information on testicular function. The main advantages in comparison with functional measures such as fertility rates and time taken to conceive are the possibilities to examine men independently of marriage and pregnancy, to find changes of fecundity with different exposures within the same person and to detect adverse effects when no alteration of fertility is yet taking place. In the implementation of an occupational sperm study considerable attention must be paid to logistic issues. A mobile laboratory unit for initial semen preparation and processing may in some situations increase worker compliance and the quality of sperm cell motility. The cross sectional design which has been used in almost all male reproductive studies so far has several severe limitations including selection bias because of differential participation, difficulties in defining a suitable reference group, and lack of information about the time dimension of the cause-effect relation. The longitudinal design deals adequately with most of these constraints. Semen samples are collected before, during, and possibly after exposure to the risk factor of interest and causal inferences are based upon change of semen variables within a man over time rather than upon differences between men. The logistics of the longitudinal study may benefit from pre-employment health examinations to enrol newly hired workers and require fewer participants to obtain comparable statistical power. In conclusion, andrological methods and epidemiological designs are available for the implementation of valid studies concerned with environmental impact on human testicular function. Occupational sperm studies should probably not be the first choice when the objective is initial screening of environmental impact on fertility but should be implemented when their is a need to corroborate or refuse earlier evidence that specific exposures have impact on testicular function.

Biomarkers↗

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↗

PubMed1999

A five-parameter logistic equation for investigating asymmetry of curvature in baroreflex studies.

Baroreceptor reflex curves are usually analyzed using a symmetric four-parameter function. We wished to ascertain the validity of assuming symmetry in the baroreflex curve and also of constraining the curves to pass through the resting blood pressure and heart rate (HR) values. Therefore, we have investigated the suitability of a new five-parameter asymmetric logistic model for analysis of baroreflex curves from rabbits and dogs. The five-parameter model is an extension of the usual four-parameter model and reduces to that model when the fitted data are symmetrical. Using 30 data sets of blood pressure versus renal sympathetic nerve activity (RSNA) and HR from six conscious rabbits, we compared the five-parameter curves with the four-parameter model. We also tested the effect of forcing these baroreflex curves through the resting point. We found that the five-parameter model reduced the unexplained variation and gave small but important improvements to the estimates of plateaus for RSNA and HR and the HR gain. Although forcing the HR curves through the resting values had little effect, this procedure, when applied to RSNA, produced a worse curve fit by increasing the unexplained variation with alteration to most of the estimated curve parameters. The mean arterial pressure-HR baroreflex relationship from six conscious dogs was also analyzed and showed clear evidence of systematic asymmetry. We conclude that the asymmetric model is a valuable extension to the symmetric logistic model when examining baroreceptor reflexes, giving improved estimates of the parameters and a new approach to examining the mechanisms contributing to baroreflex curve asymmetry. Furthermore, forcing the curves through the resting value is a statistically questionable practice when analyzing RSNA, because it affects the parameter estimates.

Animals↗

PubMed1980

Use of multiple logistic analysis in twin zygosity diagnosis.

Stochastic methods were applied to the diagnosis of twin zygosity by mailed questionnaire in a study on adult twins. Multiple logistic discriminant analysis was able to classify twin pairs previously left unclassified (XZ) by a deterministic method, and accuracy of classification was verified by blood testing. The mean intrapair differences of height and weight of XZ pairs were in between dizygotic and monozygotic pairs, but the frequency of personal contact between XZ twins was significantly less than that of MZ or DZ pairs. Both classification methods, when used separately with the same questions, left unclassified 6.5-7.6% of all 11,542 respondent pairs in the Finnish Twin Registry, but deterministic classification followed by logistic analysis misclassified only 1.9% of all twin pairs.

Adult↗

PubMed2002

Logistics of referral, diagnostic assessment and treatment of patients with breast symptoms and signs.

BACKGROUND AND AIMS: The logistics of diagnosis and treatment in a hospital with slightly above 400 new cases of breast cancer per year is analysed. MATERIALS AND METHODS: The patient flow from referral, through the diagnostic procedures and through surgical treatment is described. RESULTS AND CONCLUSIONS: The basic principle of the diagnostic assessment is the triple diagnostic procedure including mammography supplemented by ultrasonography, fine needle aspiration cytology and clinical examination. The radiologist and pathologist are working together in the breast diagnostic centre and are thus able to give a "single visit diagnosis" in most cases. The surgeon sees the patient either the same day or the next. A "consensus meeting" held each week with representatives for all specialities present has an important function in quality assurance and education. If one or more of the triple diagnostic components reach conclusion level "suspicious lesion", surgery is indicated. In hospital management is based on day surgery for all biopsies, wide excisions with or without sentinel node and some ablatio simplex mammae. For wide excision and ablation with complete axillary node clearance, the patients are transferred from the day surgery unit to a patient hotel after 3-4 hours of observation and stay till the drain can be removed. Only in rare case of high cardiopulmonary risk, beds in ordinary wards are used. This is a highly cost efficient logistic saving the hospital approximately 400,000 EUR a year compared to ordinary in hospital treatment.

Breast Neoplasms↗

PubMedDate not supplied

Predicting observed and latent responses to BLUP selection involving logistic variates.

Multivariate BLUPs can be derived when data are a mixture of continuous traits and observed discrete traits controlled by logistic latent traits. Algorithms were developed for predicting discrete responses to BLUP selection, and latent responses when the selection process included additional culling on scores. These algorithms were Taylor expansions using well-known expressions such as the probabilities and the two first moments of the truncated multinormal distribution, after appropriate re-parametrizations. They were compared to very accurate quadrature integrations. The test examples were suggested by a situation found in chickens where selection can involve body weight and leg deformity described by two logistic latent variates. Quadratic Taylor expansions generally provided a good accuracy. Therefore, they could be recommended when quadrature methods are too demanding, e.g., for complex breeding schemes.

Journal Article↗