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PubMed1977

[The proof of age differences of slow acoustically evoked potentials of adults by a multivariate statistical analysis (author's transl)].

Many authors consider the nature of the slow acoustically evoked potentials to be partly a specific one. Therefore the AEP-time behavior probably contains more information about the functional state of the acoustical channel than it is got by the usual measurement of only 3 values (N1P2-amplitude, 2 latencies). A test of this hypothesis is possible with a multivariate mathematical procedure, which involves the whole AEP-time behavior. We are using the multivariate variance- and discriminant analysis. For the application of this statistical method random samples of patients with certain otologic diseases are needed. To avoid mistakes in grouping these samples some preliminary investigations had been necessary: This paper reports the results of multivariate investigations concerning age differences of the AEP in normal hearing adults. By means of the multivariate variance analysis the AEP of 3 age groups were examined (group 1: 15--34 years, group 2: 35--44 years, group 3: 45--60 years). At 1000 Hz as well as at 400 Hz significant differences between the group averages were found, which were not detectable by the usual N1P2-amplitude measurement. Furthermore with the discriminant analysis it is possible to perform a relatively reliable differentiation between the individual AEP of the age groups 1 and 3.

Acoustic Stimulation↗
PubMed1983

Importance of mathematical models and multivariant statistical analysis for the diagnosis of ventilation disorders.

The authors present results of a comprehensive, mostly mathematical, solution of problems of the mechanism of breathing and ventilation. The need for a multivariant approach is based on the knowledge of disorders of the individual factors influencing ventilation. The authors are convinced that this approach means a useful contribution to the establishment of diagnosis and to economization of treatment.

Adult↗
PubMed1986

Vaginal colonization with Escherichia coli in healthy women. Determination of relative risks by quantitative culture and multivariate statistical analysis.

The rate of vaginal colonization with Escherichia coli in 495 healthy women was 12% in a prospective study with use of selective media and semiquantitative culture techniques. Computer-assisted multivariate analysis revealed that vaginal E. coli was significantly associated with the menstrual phase of the cycle, prior use of antibiotics, use of diaphragm or cervical cap for contraception, history of previous urinary tract infection, and coisolation of Staphylococcus aureus that was positive for the toxic shock syndrome toxin-1 (p less than 0.05, multiple stepwise logistic regression analysis). No significant association was observed with tampon use or brand, other contraceptive methods, sexual activity, genital symptoms, recent vaginal infection, or other personal habits. Quantitative cultures obtained sequentially throughout the menstrual cycle in 12 unselected women confirmed higher E. coli counts in menstrual or midcycle samples compared to paired premenstrual specimens (p less than 0.05, Wilcoxon paired rank sign test). These data emphasize the hormonal and other host determinants in vaginal colonization by E. coli and may explain the high rate of vaginal E. coli (64%), in addition to toxicogenic S. aureus, in acute toxic shock syndrome and the higher incidence of urinary tract infection in women with diaphragm or cervical cap for contraception compared to other contraceptive methods.

Adult↗
PubMed1992

Factors involved in burn mortality: a multivariate statistical approach based on discriminant analysis.

This article suggests an alternative statistical model for studying the mortality of burned patients: discriminant analysis. This model was applied to our population of 532 patients among whom 71 died. It is not the first time that this model has been applied to assess burn mortality, although it is not frequently used for that application. We found four factors that are statistically significant: age, TBSA, inhalation injury and sex (female). Discriminant analysis allowed us to demonstrate an impressive correlation between death, age and TBSA; inhalation injury by itself and sex, the two other significant factors in our study, seem to have a minor influence on the final outcome of the burned patients and their predictive value is virtually nil. The advantages of this statistical model are compared with logistic regression, the commonly chosen statistical method.

Adult↗
PubMed1984

A multivariate statistical method for the establishment of maximum allowable exposure to toxic materials in the workplace.

A model has been developed for setting standard limiting concentrations for toxic substances in the body fluid or tissues of industrial workers. The method is very flexible, and allows the use of either univariate or multivariate data, and of classification schemes which are either supervised, unsupervised, or partially supervised. An index of subclinical biological damage is derived which is used to determine an optimal limiting exposure level. The model is applied to the particular case of selecting a maximum allowable concentration of blood lead in workers in industrial settings where lead toxicity is a danger.

Analysis of Variance↗
PubMed1983

Detection and accommodation of multivariate statistical outliers.

This paper deals with the problem of identifying and testing a number of extreme sample elements (t = 1, 2, 3 and 4) as significant outliers in a sample of size n from a K-dimensional normal distribution with unknown parameters. Accommodation of detected outliers is effected through outlier-robust estimation of multivariate location (mean vector) and dispersion (variance-covariance matrix).

Analysis of Variance↗
PubMed1987

Evaluation of cataract-related risk factors using detailed classification systems and multivariate statistical methods.

The well-known different morphological features observed in so-called senile cataract are probably symptoms of various pathogenetic mechanisms in the lens. In order to identify a relationship between type of cataract and special risk factors, a cataract classification system using Scheimpflug photography has been developed. Data of 288 cataract patients (case histories and blood chemistries) have been grouped according to differences in cataract morphology. The multivariate analyses showed the following five variables to be important and to contribute independently to the differentiation of cataract types: cholelithiasis, allergy, heart insufficiency, pneumonia, and age. A case-control study without consideration of cataract morphology showed the following variables to be important and to associate independently with the risk of developing cataracts: age, allergy, diabetes, hypotension, hypertension, use of analgesics, and coronary disease.

Age Factors↗
PubMed1976

Comparison of Frank's and McFee's lead systems using multivariate statistics.

Two widely used orthogonal corrected 3-lead system - the Frank and the McFee systems - were studied in order to evaluate whether a significant difference in diagnostic performance could be observed; in the case of a positive answer, we would be able to advocate one system instead of the other. No such overall difference was noticed. Although +/- 17% discrepancies were found on the individual classification level (a patient correctly classified with system A and missed with system B and conversely), the practical implication is negligible since each system is responsible for +/- half of these discrepancies. Multivariate analysis, as already largely proved by Pipberger's group, drastically ameliorates the diagnostic results. Special caution has been given to the number of selected discriminators in order to enhance repeatability of the results; the reproducibility, using the approach developed by Cornfield, was found excellent. Some particular features as to the choice and location of the best discriminators were found somewhat puzzling by the autors but no deterministic explanation could be offered: the selection of the variables, indeed, rested on statistical bases and not on the (sometimes fragmentary) knowledge of what is going on in the heart and how these events relate to surface waveform patterns.

Adult↗
PubMed1988

Evaluation of corrective surgery for tetralogy of Fallot from late results by multivariate statistical analysis.

From 1966 to 1985, 469 pediatric patients with the tetralogy of Fallot (mean age, 4.9 years) were corrected (hospital mortality 11.9%). There were 9 late deaths (1.9%). In 186 patients, hemodynamic studies were performed 2-14 years postoperatively (mean age, 10.4 years). An increased cardiothoracic ratio (CTR) of 60% or more was found in 42 patients with impaired postoperative physical activity. The factors affecting the late results were investigated in relation to CTR by the quantification method of multivariate analysis. As for the enlarged CTR, pulmonary regurgitation was more of a contributing factor than pulmonary stenosis. In pulmonary regurgitation, the pulmonary artery area index (PAAI) and reconstruction of the right ventricular outflow tract (RVOT) were highly significant factors. For pressure gradient, the VSD site was the most significant factor. These analyses suggest that preservation and/or reconstruction of the pulmonary valve, or trans-annular patching with the necessary minimal area for the RVOT (PAAI) not to exceed 4 cm2/m2 at the time of operation is important for satisfactory late results.

Adolescent↗
PubMed1985

Coronary risk factors and their pathway of action through coronary raised lesions, coronary stenoses and coronary death. Multivariate statistical analysis of an autopsy series: the Oslo Study.

From 1972 to 1973, 16,202 Oslo men, aged 40 to 49 years, were examined for cardiovascular disease and coronary heart disease (CHD) risk factors. This report describes the results of autopsy examinations from 204 of 471 men who died in this cohort with regard to associations between selected risk factors and (1) raised coronary atherosclerotic lesions (RL), (2) coronary artery stenosis, and (3) CHD death. Total serum cholesterol and blood pressure levels were positively associated with all 3 measures of coronary atherosclerosis and its complications, both in univariate and multivariate analyses, whereas high-density lipoprotein (HDL) cholesterol was highly and inversely related. Triglyceride levels, cigarette smoking, social class and physical activity at work and at leisure were not significantly associated with either of the 3 measures. When RL was added to the model with stenosis as the dependent variable, the risk factors no longer appeared as independent; this is consistent with the hypothesis that these factors, when significant, work through the development of RL to produce stenosis. HDL cholesterol was the only risk factor independently and significantly associated with CHD death when RL or stenosis or both were put into the model for CHD. This points to the possibility of HDL cholesterol also working through mechanisms other than the prevention of RL and stenosis toward CHD death.

Adult↗
PubMed1976

Quantitative studies of single-cell properties in monkey striate cortex. V. Multivariate statistical analyses and models.

1. Several statistical analyses were performed on 205 S-type and CX-type cells which had been completely analyzed on 12 response variables: orientation tuning, end stopping, spontaneous activity, response variability, direction selectivity, contrast selectivity for flashed or moving stimuli, selectivity for interaction of contrast and direction of stimulus movement, spatial-frequency selectivity, spatial separation of subfields responding to light increment of light decrement, sustained/transient response to flash, receptive-field size, and ocular dominance. 2. Correlation of these variables showed that within any cell group, these response variables vary independently. 3. A multivariate discriminant analysis showed that orientation specificity, receptive-field size, interaction of direction and contrast specificity ocular dominance, and spontaneous activity, taken together can adequately assign cells into the S-type or CX-type subgroups. 4. Various models of visual cortex are examined in view of the findings reported here and in the previous papers of this series, which suggest that a) orientation and direction selectivities are produced by separate neural mechanisms, b) there may be hierarchy among simple (S type) cells, and c) complex (CX-type) cells appear to receive a prominent S-type cell input.

Animals↗
PubMed1990

Variation of movement characteristics with washing and capacitation of spermatozoa. II. Multivariate statistical analysis and prediction of sperm penetrating ability.

Fifty semen samples were studied by computer-assisted semen analysis before testing in the sperm penetration assay (SPA). Twenty-one concentration and movement measurements were obtained from each sample on sperm in semen, after washing and swim-up, and again after an 18-hour capacitation period. Discriminant analysis was then used to define a function from these measurements that would classify the SPA results as above or below a 10% penetration rate. A significant function was identified using the following variables: sperm concentration and motility in semen, and mean curvilinear velocity, linearity, and amplitude of lateral head displacement of washed sperm. Movement measurements of capacitated spermatozoa were not useful predictors in this analysis. The overall accuracy of this function for predicting SPA results was 72%. These findings demonstrate that computer-derived measurements of sperm movement provide biologically useful information regarding sperm function, and, in addition, emphasize the importance of multivariate techniques in the analysis and description of human sperm motion.

Analysis of Variance↗
PubMed1990

Classification of glucose-6-phosphate dehydrogenase variants by multivariate statistical analysis.

Using principal component analysis a two-dimensional presentation of kinetic parameters from various G6PD-variants was obtained from which similarities between individual enzymes became detectable. Conclusions could be drawn as to how far the kinetic parameters contribute to the discrimination between different variants. An objective classification of G6PD-variants was achieved by application of cluster analysis. The proposed methods provide an effective means for differential elucidation of G6PD-variants and other heterogeneous enzymopathies.

Cluster Analysis↗