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Results for “multivariate analysis”

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At least 19 recordsLinked to original sources

PubMed1977

Changes of P50 in hypoxaemia, hypercapnia and polycythaemia: multivariate analysis.

Multivariate analysis of P50 changes in hypoxia, hypercapnia and polycythaemia was performed in an heterogeneous group of forty three patients: hypoxic subjects with or without hypercapnia, with or without polycythaemia and polycythaemic subjects without hypoxia. A statistical analysis was undertaken using comparison of the means, study of the correlations, principal component analysis, multiple regression and correspondence analysis. In the patients studied, P50 changes were not wholly explained by those of 2-3 DPG and pH; PaCO2, per se, did not play an important part. Haemoglobin concentration and P50 value would represent an adaptative mechanism to hypoxia: when hypoxia is moderate (80 greater than PaO2 greater than or equal to 65 torr) and isolated, oxygen haemoglobin affinity decreases (P50 increases); when hypoxia is severe (PaO2 less than 65 torr) and combined with hypercapnia and disturbed acid-base equilibrium, P50 comes back to normal range but haemoglobin increases, restoring thus, the normal blood oxygen content.

Adult↗

PubMed1977

Structural analysis of the ridge count data of Australian Europeans using multivariate analysis.

Multivariate analyses are used to study the structural patterns of ridge counts of fingers. There is a significant difference between the ridge counts of two hands, chiefly due to the first and fourth fingers. There is asymmetry in the covariance matrix of the ridge counts. The correlations between fingers are significant and the decrease in correlation with increasing distance between fingers is not significant.

Australia↗

PubMed1979

Risk assessment of pulmonary embolism by multivariate analysis.

A prospective study of 6,527 hospitalized patients was performed to evaluate the effectiveness of multivariate analysis of risk factors to correctly designate risk for pulmonary embolism. History of previous pulmonary embolism was the single most important factor. In patients without prior history, five factors emerged: inactivity, congestive heart failure, Doppler ultrasound evidence of deep-vein occlusion, female sex, and black race. Used together, these factors permitted a discrimination of risk such that 68.7% of pulmonary embolization was found to occur in 32.2% of the population designated as showing increased risk. Multivariate analysis of clinical factors improved assessment of risk, compared to the use of lower extremity findings alone, and proved to be useful in identifying individuals at increased risk for pulmonary embolism.

Analysis of Variance↗

PubMedDate not supplied

[Multivariate analysis of aminoacyl-tRNA synthetase activities of liver and hepatomas (author's transl)].

Data on the aminoacyl-tRNA synthetase activities in normal liver and in three transplantable rat hepatomas, viz Yoshida's AH 130 and Morris's 5123C and 7793, were studied by means of factor analysis, a powerful technique of multivariate analysis particularly suitable foridentifying factors which theoretically may account for the pattern of interrelations between several variables. The analysis has been performed on 51 patterns of enzyme activities, covering 17 out of the 20 aminoacyl-tRNA synthetases; 80% on average of the total variability of the 17 enzyme activities may be accounted for by the first 4 factors extracted. The enzymes seem to fall into different groups, depending on their relationship with the factors thus identified. The results suggest that enzymes belonging to the same group share a common control mechanism, and are independent of the enzymes belonging to different groups, both in normal liver and in hepatomas.

Amino Acyl-tRNA Synthetases↗

PubMed1976

Subjective multivariable analysis bu computer for evaluation of coronary artery bypass.

Subjective multivariable analysis by computer was utilized to evaluate the results in a series of 659 patients undergoing coronary artery saphenous vein bypass surgery. A video terminal gave access to a remote computer. The postoperative subjective response was evaluated by questionnaires sent to patients at 6- to 12-month intervals, and was augmented by treadmill testing and postoperative coronary arteriography. Operative risk and subjective response are related only to the degree of ventricular function lost prior to surgery. Long-term results were best in patients in whom complete revascularization was possible. Current operative risk is less than 1%; a five-year survival rate of 90% to 95% is predicted. More than 90% of patients were asymptomatic or "greatly improved." Postoperative treadmill tests were negative in 88% of patients in these groups. In patients who were only "slightly improved" or "not improved," repeat catherization showed a graft patency rate of 84%, suggesting that recurrent symptoms were related to the extent of preoperative disease or to the progression of disease in nongrafted vessels, rather than to graft occlusion.

Computers↗

PubMed1978

Continued use of contraception among Philippine family planning acceptors: a multivariate analysis.

The factors that contribute to continued use of contraception are examined through a multivariate analysis of data gathered in the course of the Philippine 1974 National Acceptor Survey. Twenty-five independent variables were utilized in the analysis, of which only three were found to have an appreciable effect upon continuation: the method accepted, age, and husband's attitude regarding family planning. When the sample was divided into method subgroups, several features of the service process explained variance in pill continuation, and fecundability explained variance in rhythm continuation. The findings suggest that there is considerable potential for improving the effectiveness of the Philippine program through administrative action. Better IUD services and information, more emphasis on the needs of husbands, and improvements in the ongoing support of pill users could substantially improve the amount of contraceptive protection offered by the program.

Adolescent↗

PubMed1975

The ascent of man: deductions based on a multivariate analysis of the brain.

This paper attempts to investigate taxonomic and phylogenetic relationships through an analysis of the distribution of mass within the brain. A multivariate analysis was performed on encephalization ratios for various divisions of the brain, employing volume measurements reported for 63 species by Stephan et al. [1970]. The ratios for each brain region were considered to lie along one of the dimensions of eight dimensional 'brain space', and distances between all species were calculated and employed in the determination of 'family trees'. It was assumed that modern species have, in many cases, brains representative of different stages of an evolutionary progression towards higher encephalization, and it was assumed that no 'backwards evolution' occurred. The family trees based on these data and assumptions were rigidly determined and do not represent mere opinion but, rather, inescapable conclusions if one accepts the premises. Most of the findings were in very good agreement with traditional or popular ideas, and this includes conclusions that tree shrews were ancestral to prosimians and that simians are derived from a tarsioid ancestor. Other findings, however, were just as strikingly deviant from current popular and expert thought. Present methods demanded, for example, that man must have a platyrrhine ancestry. While one may reject this particular conclusion it remains true that by present measures the human brain is much more like that of an American wooley or spider monkey than like that of either the chimpanzee or the gorilla.

Amygdala↗

PubMed1975

Multivariate analysis: the need for data, and other problems.

Multivariate analyses are an aid to, not a substitute for critical thinking in the area of data analysis. Meaningful results can only be produced by these methods if careful consideration is given to questions of sample size, variable type, variable distribution etc., and accusations of subjectivity in interpretation can only be overcome by replication. The computer revolution has produced many problems for statisticans, not least of which is the ease with which experiments may access packages of programs for multivariate analysis, and so bypass a "difficult" (by which is meant one who will not do simply as he is told) statistician. Of course there are many abusers of univariate statistical methods. Here, however, the abuses are not likely to lead to such seriously misleading results as in the multivariate case. Perhaps a major cause of the continuing misuse of statistical methods is the insistence of many journal editors in psychology and related areas, on articles being laced with multivariate analyses, and on encouraging the pedantic use of signifance levels, i.e. the inevitable p less than minus, as if such inclusions lent an air of respectability to their journal which it might not otherwise have had. Research workers in these fields would be better encouraged to devote more time to an initial screening of their data using simple graphical techniques, to ensure that their data are at least approximately suitable for more complicated multivariate analyses.

Psychiatry↗

PubMed1977

Multivariate analysis of the septal syndrome.

Since recent reviews of the behavioural effects of septal lesions agree that more than one explanatory concept is required, a multivariate analysis of the septal syndrome has been made. A total of 127 rats have been tested 73 with septal lesions and 54 controls. The rats were tested in a standard test battery consisting of a residential maze, spontaneous alternation, spatial learning, approach/avoidance conflict and one-way active avoidance. Factor analyses reveal a complex change in the factor structure after septal lesions. None of the previous explanations of septal functions receives unequivocal support. The findings do not exclude the possibility that septal lesions interfere with a few general behaviour mechanisms or perhaps only one. However, if so, this factor does not explain as much of the variance as expected. Situational or test-dependent factors play a greater role in the variance. This is interpreted as an indication of insufficiency in the theoretical structure, or in conventional test designs.

Animals↗

PubMed1976

Angina pectoris among 10,000 men. II. Psychosocial and other risk factors as evidenced by a multivariate analysis of a five year incidence study.

The major independent role played by anxiety and severe psychosocial problems (especially family ones) is demonstrated by this multivariate analysis of a five year prospective study of the development of new angina pectoris among almost 10,000 adult men (average annual incidence = 5.7/1,000). The independent effect of these two variables is considerably augmented by the other significant risk factors of age, total serum cholesterol, systolic or diastolic blood pressure, certain electrocardiographic abnormalities and diabetes mellitus. The presence of all seven risk factors (at a high level) increases the probability of angina pectoris developing within five years to 289/1,000 from 14/1,000, when these factors are low or absent. The wife's love and support is an important balancing factor, which apparently reduces the risk of angina pectoris even in the presence of high risk factors. The implications of these findings to the pathophysiology and prevention of angina are stressed.

Adult↗

PubMed1979

Short-term prognostic index in acute myocardial infarction. Multivariate analysis by Cox model.

A new multivariate stepwise linear regression analysis (Cox's model) with survival time as prognostic endpoint was utilized in 281 patients with acute myocardial infarction. From 18 prognostic factors occurring during the first 5 days in the Coronary Care Unit a new prognostic index was calculated for the chance of survival in the first 36 days after admission. The significant prognostic variables were heart failure, cardiogenic shock, atrioventricular block and age. The total group of patients was classified in 6 subgroups with different mean indices and prognosis. There were 2 large groups of patients with relative bad and good prognosis (with and without heart failure). Over half of the patients had no prognostic variables. There was a trend of overestimating the expected deaths. A definite cardiac cause of death was shown by 23 patients (82%). This prognostic index based on the 4 variables can for the individual patient predict the chance of survival, which can be the basis of an individualized duration of hospital stay.

Age Factors↗

PubMed1975

Multivariate analysis in the pharmacological evaluation of a saluretic compound.

The pharmacological evaluation of the diuretic activity of a compound -- performed measuring the urinary volume and determining its electrolyte content -- may be usefully integrated by a multivariate analysis, in order to: express a general evaluation for each animal in terms of positive or negative response; evaluate the false positive responses of the control group animals and the negative responses in the treated animals on the basis of the general response. An example of application relating to a well-known saluretic, 4-chloro-N-(2-furfuryl)-5-sulfamoyl-anthranilic acid (furosemide), is reported.

Analysis of Variance↗

PubMed1975

Epidemiological evaluation of funduscopic findings in cerebrovascular diseases. II. A multivariate analysis of funduscopic findings.

The interrelationship of the funduscopic, physical and laboratory findings, the additional information of each funduscopic finding when physical and laboratory findings were considered simultaneously, and the relative importance of each retinal finding in the funduscopic pictures were investigated by a series of multivariate analysis for 68 cerebral hemorrhage, 47 cerebral thrombosis and 230 controls in two rural towns, Akabane and Asahi, in Japan and the results were as follows: 1. For the occurrence of cerebral hemorrhage, narrowing of arteriole and irregular constriction were especially important indicators, and retinal bleeding and lateral displacement were also valuable but less than narrowing and irregular constriction. On the other hand, for the occurrence of cerebral thrombosis, arteriolar reflex was considered as the most valuable indicator, and irregular constriction, lateral displacement and white plaque were also important but less than arteriolar reflex. 2. Narrowing of arteriole was most highly related with irregular constriction while the correlation between retinal bleeding and white plaque, and also the correlation between arteriolar reflex, vertical and lateral displacement and tapering were significant. 3. A significiant correlation among physical and laboratory findings was found only between systolic and diastolic blood pressure as far as analysed. Funduscopic findings by Scheie's hypertensive and Keith-Wagener's classifications were highly correlated with systolic and diastolic blood pressure. 4. Narrowing and irregular constriction were significantly correlated with systolic and diastolic blood pressure, and the relation between retinal bleeding and glycosuria was significant. 5. An analysis of the additional information of each funduscopic finding, when evaluated with the physical and laboratory findings simultaneously, revealed that irregular constriction, lateral displacement and narrowing gave prominent additional information for the occurrence of cerebral hemorrhage, while arteriolar reflex, lateral and vertical displacement and white plaque gave valuable information for the occurrence of cerebral thrombosis. 6. It is noteworthy from these multivariate analyses that narrowing and irregular constriction may arise from a similar pathophysiological mechanism which brings out vasoconstriction and the resultant organic changes due to hypertension. It is also noticed that arteriolar reflex and A/V crossing phenomenon may come from the different pathophysiological mechanism related to arteriosclerosis. It was stressed that detailed analyses of observer variability and evolution of funduscopic findings would be necessary.

Albuminuria↗

PubMed1978

Prognostic factors in cutaneous malignant melanoma in stage I. A clinical, morphological and multivariate analysis.

In a retrospective study of 324 cutaneous malignant melanomas in stage I, treated during the years 1959-74, the influence of different morphological and clinical factors on the prognosis was investigated. 223 patients with melanoma in levels II-V, observed for more than five years, were subjected to a multivariate analysis. 180/223 were in levels III-V. The age of the patient, the location of the tumour, its diameter, thickness, infiltration level, presence of ulceration and mitotic activity were shown to be of significant importance for the five-year survival of the 223 patients. Analysis limited to levels III-V disclosed that the diameter and the thickness of the tumour but not the infiltration level significantly influenced the prognosis. However, the sex of the patient, the histogenetic type of the tumour, the cross-sectional profile, vascular invasion and degree of lymphocytic infiltration did not correlate with survival.

Adult↗

PubMed1979

Spike separation in multiunit records: a multivariate analysis of spike descriptive parameters.

Variables describing unit discharges from multiunit extracellular records were treated, using multivariate statistical analysis for further automatic spike separation. A spike was described by 8 parameters (3 amplitude values, 3 time values and 2 slopes). These 8 parameters were summarized by 2 new independent factors, the principal components (PC). Examination of the 2 PCs from each spike allowed the observer to determine PC families corresponding to spike populations. From these the spikes were automatically classified. PC analysis showed groups of redundant parameters. Elimination of redundancy decreased the computing time without lowering the separation efficiency of the method. Three parameters turned out to be sufficient for spike discrimination: the maximum and the minimum amplitudes and the time between these. This agrees well with the physical basis of current propagation in the conducting medium, from the firing neurone to the recording electrode.

Action Potentials↗

PubMed1978

Defects of the central nervous system in Finland: V. Multivariate analysis of risk indicators.

Based on the Finnish Register of Congenital Malformations a search was undertaken for associations between defects of the central nervous system [CNS] and various selected risk indicators. The study material consisted of 710 cases of CNS defects and their time-area matched pair controls. 259 cases of polydactyly and their controls were also compared with a view of demonstrating the possible biases introduced by the case-control method. The present report is a multivariate analysis of previously observed associations, and the linear logistic regression model was used for the elimination of confounding factors. Risk indicators remaining after the analysis were high maternal age, multipara with previous stillbirths and defective children, especially defects of the CNS. Maternal influenza, especially in combination with the intake of salicylates, was also associated with an increased risk.

Central Nervous System↗

PubMed1979

Multivariate analysis of the risk of glaucomatous visual field loss.

In a retrospective study, 92 patients with ocular hypertension, ie, intraocular pressure of 21 mm Hg or higher, and no evidence of glaucomatous visual field defects, were observed for five years. Visual field defects developed in one or both eyes of 33 patients during the five-year follow-up period, while none were detected in the remaining 59. Values for suspected risk factors, determined at the outset of the follow-up period, were subjected to a multivariate analysis with use of linear discriminant analysis and a multiple logistic function. Models of risk providing maximum separation of the two patient groups (visual field loss vs no visual field loss) found that the risk factors having the greatest significance for prediction of visual field loss included vertical estimates of cup/disc ratio, mean IOP during the period of observation, a positive family history of glaucoma, and age. Factors having the lowest predictive values included IOP response to topical dexamethasone, plasma cortisol suppression, and a history of systemic hypertension.

Glaucoma↗

PubMed1979

A multivariate analysis of fatness and relative fat patterning.

Skinfold measurements (triceps, subscapular, suprailiac and medial calf) in four samples (376 boys, 352 girs, 338 men and 380 women from rural Colombia) were subjected to principal components analysis to identify components of obesity and relative fat patterning. Three components emerged which were similar in the four samples: a first component of fatness explaining 70-80% of the variance and two fat pattern components each explaining 10-15% of the variance: trunk-extremity and upper-lower body. Fatness and the trunk-extremity pattern components changed with age in children (7-12 years), but none of the components changed with age in adults (25-60+). The fatter tended to be more patterned in both age groups. Canonical correlation analysis revealed that socioeconomic status was more related to fatness than to patterning. With the exception of brothers, all first degree relatives (sib, parent-off-spring) and spouses were correlated in fatness. Some of the correlations between relatives--usually sibs, but not spouses--were also significant for the pattern components, suggesting a genetic basis for the known stability of this characteristic (Garn, '55a). Principal components analysis is a useful multivariate alternative for quantitative studies of anthropometric patterning.

Adipose Tissue↗