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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).
Conventional Z maps provide probability statements about the deviation of observed values from the norm. Galán et al. (1994) introduced Simultaneous Significance Probability Scales to detect abnormalities over the whole map, making use of the information provided by the topographic structure of dependencies. They also described multivariate brain electromagnetic (MBE) maps for compact presentation of complex spatio-temporal information. In this paper, using the distance-based localization receiver operating characteristic curves (DL-ROC curves), we compare the localization provided by computed tomography with that provided by Z and MBE maps in 61 patients with brain lesions. Maps were calculated for absolute power and relative power in delta, theta, alpha and beta bands for voltage and current source densities (CSD). In each patient, all maps were compared and the map with the highest value of the area of the DL-ROC curve was considered to be the "best map." Z maps of CSD were the "best maps" in 24 patients. In the voltage montage, we observed that multivariate maps add some information not contained in the Z maps. However, for CSD, Z maps were more accurate than multivariate maps. A very consistent finding was the observation that lesions were better detected by maps analyzing the delta band, while edema was better represented by maps in the theta range.
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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.
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.
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.
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.
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.
Brain Electromagnetic Topography (BET) has attained widespread use. The representation of EEG or MEG parameters as scalp maps (BETm) aids its clinical interpretation. However, some critical issues limit the usefulness of BETm. In particular, the conventional statistical assessment of BETm with respect to normative data is based upon marginal significance probability scales which involve multiple univariate comparisons (one at each recording site). As a consequence, the probability of false positive findings (type I error) is increased above its nominal level. The use of conservative levels avoids this phenomenon but results in a considerable increase of the probability of not detecting real abnormality (type II error). Furthermore, BETm are constructed without taking into consideration the patterns of correlations characteristic of electromagnetic data under normal states of brain functioning. This limits the capability of BETm of representing multivariate aspects of abnormality. This paper introduces some techniques to approach these difficulties. Multivariate Brain Electromagnetic Topographic maps (MBETm) are defined, which retain the attractive features of mapping but also take advantage of multivariate characteristics (in the spatial and frequency domains) to highlight aspects of neuropathology. Moreover, simultaneous significance probability (SSP) scales, valid for both BETm and MBETm, are introduced for the global control of the probability of a type I error. The use of these techniques is illustrated with data from patients with cortical tumours and with epilepsy. ROC analysis shows that in some cases there is a significant improvement in both detection and localization accuracy.
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.
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.
Data published in international papers were analyzed and submitted to a multidimensional variate and discriminant analysis. In this analysis, information on prodromal symptoms and on hematological alterations 24 hours after irradiation was considered. As a result of the analysis it was pointed out that by means of a discriminant function the classification of persons to the four degrees of radiation sickness is possible with a computed false rate of classification of nearly 20% and a dose-effect-relation exists between discriminant scores and computed whole-body doses.
Multifactorial statistical analysis was used to identify differential diagnostic cytological features of glandular hyperplasia, atypical hyperplasia and well-differentiated adenocarcinoma of the endometrium. Twelve cytological features were identified for calculating linear discriminant function. The effectiveness of the diagnostic algorithm depends upon the diagnostic value of the sample and proficiency of the cytologist.
A great deal of information on short-term mutagenicity assays presently exists, having been generated through individual as well as large comparative programs. The comparative programs have often examined the same tests, but with different sets of chemicals; this then gives rise to the problem of how to identify the information which is common to the different data bases, i.e., the general properties of the assays. This paper continues previous analyses of this subject, and describes a general approach by which different and heterogeneous data bases can be compared to each other. The results relative to 4 assays (Salmonella typhimurium gene mutation, mouse lymphoma L5178Y cell gene mutation, chromosomal aberrations in CHO cells, and SCEs in CHO cells) in 4 different data bases were studied. Factor analysis was used to model the different pieces of information. The analysis demonstrated a concordance between the indications of the U.S. National Toxicology Program and the International Program for the Evaluation of Short-Term Tests for Carcinogens, whereas the results of Gene-Tox and the International Program for Chemical Safety turned out to be biased, to different degrees, by their specific aims and characteristics. Moreover, the general properties--independent of the specific data bases--of the 4 assays were highlighted, and the similarities between the performances of the assays were given a quantitative measure.
The conditions and the intestinal processes responsible for the action of lactose as a potential dietary fibre are described. The beta-galactosidase activity in the rat caecum and colon is influenced by dietary factors: It declines with increasing lactose concentration and it rises with increasing protein and phosphate concentration in the diet. The enzyme activity correlates negatively with the content of lactose, and positively with the content of protein and phosphate in the chymus. The products of lactose hydrolysis are degraded by microbial glycolysis in caecum and colon. The glycolytic products are mainly absorbed and energetically utilized by the macroorganism. Phosphate stimulates the microbial metabolism and, therefore, accelerates the consumption of the energy substrate lactose. Mathematical optimization gives the necessary composition of the diet which causes an intended microecological effect. To minimize the chymus pH (5.1 in the colon ascendens; 4.6 in the colon descendens; 4.3 in the faeces) the lactose content of the diet has to be greater than or equal to 160 mumol/g, the protein content less than or equal to 10 mg/g, and the phosphate content less than or equal to 5.5 mumol/g. The minimal pH value depends to a greater extent on variations in the supply of protein and phosphorus with the diet whereas the response to changes in lactose concentration is less noticeable.
To evaluate the effectiveness of Alpha-blockers, TUI-P and TUR-P in the treatment of obstruction due to BPH, 50 patients, never before treated, were considered. Fifteen were treated with alfuzosin chlorhydrate 7.5 mg/day for four months, 15 were submitted to TUI-P and 20 to TUR-P. In all patients linear purr was carried out before treatment and was repeated from 60 to 90 days after intervention in surgical patients and during the fourth month of treatment in patients treated with alfuzosin. The data obtained were analyzed with the T-test both for dependent and independent samples. The results show that Alpha-blocker contain an increase in maximal flow, without decreasing bladder voiding pressures. On the contrary TUI-P and TUR-P, besides the increase in maximal flow obtain a significant reduction of bladder pressures. The conclusions are the following: maximal flow alone is not a sufficient parameter to evaluate the work of the bladder, the entity of the obstruction and the effectiveness of the therapy. The treatment with Alpha-blockers is unable to reduce the obstruction due to BPH. TUI-P and TUR-P realize an effective deobstruction. Under the same deobstructing effect TUR-P assures a better voiding performance by obtaining higher flow values.
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