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PubMed2004

(Mis)use of factor analysis in the study of insulin resistance syndrome.

Over the last decade, factor analysis has been used increasingly to describe patterns of simultaneous occurrence of the central components of the insulin resistance syndrome. In this paper, the authors describe factor analysis, review studies that have used factor analysis to examine the insulin resistance syndrome, and explore how factor analysis might be used to increase our understanding of this syndrome. Most studies that they reviewed gave vague reasons for using factor analysis and did not demonstrate an understanding of the use and limitations of this statistical method. Confirmatory factor analysis based on sound theoretical concepts and a clear understanding of the statistical methods may provide some insights into the pathophysiology of the syndrome. However, to date none of the studies has adopted this approach, and other statistical approaches and study designs are likely to provide greater understanding of the syndrome.

Factor Analysis, Statistical↗
PubMed1978

Development of an index of health utilizing factor analysis.

A multivariate technique, factor analysis, was used to calculate an index number for each county in Mississippi and an overall state index number for the year 1970. Data on 55 indicators of health were factor analyzed (Principal components, Varimax rotation) and eight factors were extracted. These eight factors were identified as Resource population, Economics, Geriatrics, Social problems, Preventive medicine, Nutrition, Mortality, and Disability. Sixty-two per cent of the total variance was explained by these factors. The index numbers were standardized as percentages for ease of comparison across all 82 counties. Therefore, a multivariate technique has been used to quantify the elusive multidimensional term "health" and that is something which has not previously been adequately accomplished.

Factor Analysis, Statistical↗
PubMed1986

Enhancement of physiological factors in factor analysis of dynamic studies.

Factor analysis of dynamic radionuclide studies provides their decomposition into the images and time-activity curves corresponding to the underlying dynamic structures. The method is based on the analysis of study variance and on the subsequent differential imaging of its principal components into a simplified factor space. By changing the amount and the composition of the variance processed in the analysis it is possible to enhance the factors that are important for diagnosis while the less important factors can be suppressed. In our report, a short theoretical review of the problem is given and illustrated by the analysis of dynamic cholescintigraphy. It is shown that a suitable choice of region and/or the temporal interval of interest enables the differential evaluation of such intrahepatic compartments, which could not be observed without enhancement.

Calculi↗
PubMed2006

Long-term stability of food patterns identified by use of factor analysis among Swedish women.

Limited data exist on the reproducibility of food patterns measured by factor analysis as well as on the use of stability of patterns over time. Our primary objective was to explore the long-term stability of food patterns derived by confirmatory factor analysis among 33,840 women participating in the Swedish Mammography Cohort. Our secondary objective was to compare factor solutions from confirmatory factor analysis with those derived by use of exploratory factor analysis. Diet was assessed by a food frequency questionnaire in 1987 and 1997, and food patterns were derived by the use of exploratory and confirmatory factor analysis. We observed four major food patterns (Healthy, Western/Swedish, Alcohol, and Sweets) at both time points. Correlations between confirmed food patterns in 1987 and 1997 were 0.37 for the Healthy pattern, 0.27 for the Western/Swedish pattern, 0.54 for the Alcohol pattern, and 0.44 for the Sweets pattern (P < 0.0001 for all associations). Patterns derived by the use of exploratory factor analysis were strongly associated with those derived by the use of confirmatory factor analysis (r >/= 0.90, P < 0.0001, for all associations). The patterns derived in this study were similar to those derived in other studies, indicating reproducibility of food patterns across populations. Our study suggests that food patterns measured by the use of confirmatory factor analysis are reproducible over time, and weaker correlations observed may reflect natural changes in eating behavior, the food supply, and/or perceptions of what is considered healthy. Testing whether patterns measured over a long time period can be used in analytic studies is the next step in assessing the validity of this method.

Alcohol Drinking↗
PubMed2000

Invited commentary: insulin resistance syndrome? Syndrome X? Multiple metabolic syndrome? A syndrome at all? Factor analysis reveals patterns in the fabric of correlated metabolic risk factors.

Factor analysis has emerged as a useful method for understanding patterns underlying the co-occurrence of metabolic risk factors for both type 2 diabetes and atherosclerosis--often referred to as "insulin resistance syndrome." In factor analysis of data on 322 healthy elderly people from the Cardiovascular Health Study, Sakkinen et al. (Am J Epidemiol 2000;152:897-907) confirmed findings from a dozen prior studies that as many as four distinct physiologic domains comprise the syndrome, with a unifying role for markers of insulin resistance. With the addition of markers of hemostasis and inflammation, they also found that impaired fibrinolysis and endothelial dysfunction are central features of the syndrome, while inflammation is only weakly linked to insulin resistance through associations with obesity.

Arteriosclerosis↗
PubMed1990

[Factor analysis in thallium-201 chloride thyroid studies].

Factor analysis was applied to thyroid thallium-201 imaging to get separated image of tumor from normal thyroid tissue. Thirty-eight patients with various thyroid tumors which were histologically confirmed were included in this study. Following intravenous injection of 111 MBq (3 mCi) of 201Tl chloride, thyroid images in 64 frames were taken for 30 to 60 minutes using Toshiba gamma camera system and data were analyzed by 2 or 3 factor analysis. In 28 of 38 patients separated images of the lesions from normal thyroid were obtained and time-activity curves of various shapes corresponding to the lesions were also obtained. When the curves were classified into 3 groups according to their shapes: increasing, flat and decreasing, follicular carcinoma did not show increasing shape whilst neither of papillary carcinoma, squamous cell carcinoma and anaplastic carcinoma showed decreasing shape. The shapes of the curves were thought to be reflected in clearance of the agent from the lesions. Factor analysis in 201Tl chloride thyroid scan provided separated image of tumor from normal thyroid gland automatically and the obtained curves corresponding to the lesions provided information for estimating the characteristics of thyroid tumors.

Adult↗
PubMed2005

Source identification of fine particles in Washington, DC, by expanded factor analysis modeling.

An expanded factor analysis model (ME-2) that is capable of taking into account the influence of independent variables such as wind speed, wind direction, time of year and other variables of the measured fine particle matter (PM2.5) concentration data was utilized for identifying sources of airborne pollutants and providing quantitative estimations of the contribution of each source. The chemical composition data used in this study were obtained from PM2.5 samples collected using the Interagency Monitoring of Protected Visual Environments samplers from August 1999 to December 2001 at an urban monitoring site in Washington, DC. The expanded model has been applied to two different data sets based on the particulate carbon variables. Such an approach had been successfully applied previously and provided improved source resolution in simulated and ambient concentration data. Initially, total OC and EC were used in the expanded model and were compared to the results using conventional positive matrix factorization that had been done previously using the individual carbon fractions data. In the other expanded model analysis, the eight carbon fractions were used during the modeling in order to ascertain if additional source information could be extracted from the data. In both cases, it was possible to separate diesel from spark-ignition vehicles. The use of the individual carbon fractions in the model provides information on what appears to be secondary organic aerosol formation.

Air Pollutants↗
PubMed1991

Salivary SPECT and factor analysis in Sjögren's syndrome.

Salivary SPECT and factor analysis in Sjögren's syndrome were performed in 17 patients and 6 volunteers as controls. The ability of SPECT to detect small differences in the level of uptake can be used to separate glands from background even when uptake is reduced as in the patients with Sjögren's syndrome. In control and probable Sjögren's syndrome groups the uptake ratio of the submandibular gland to parotid gland on salivary SPECT (S/P ratio) was less than 1.0. However, in the definite Sjögren's syndrome group, the ratio was more than 1.0. Moreover, the ratio in all patients with sialectasia, which is characteristic of Sjögren's syndrome, was more than 1.0. Salivary factor analysis of normal parotid glands showed slowly increasing patterns of uptake and normal submandibular glands had rapidly increasing patterns of uptake. However, in the definite Sjögren's syndrome group, the factor analysis patterns were altered, with slowly increasing patterns dominating both in the parotid and submandibular glands. These results suggest that the S/P ratio in salivary SPECT and salivary factor analysis provide additional radiologic criteria in diagnosing Sjögren's syndrome.

Adult↗
PubMed1990

[Assessment of different clearance mechanisms of the lung using factor analysis].

Measurement of epithelial clearance over the lungs is always influenced by mucociliary transport since the lung is a 3-dimensional organ where ciliated and respiratory epithelia overlap. Factor analysis provides factor images and time-activity curves of extracted physiological factors corresponding to specific structures, even if these structures overlap. In 16 inhalation studies of 99m Tc-DTPA aerosol, factor analysis always extracted 2 factors with opposite temporal behavior, one corresponding to epithelial and one to mucociliary transport. Clearance rates measured over the lungs were significantly lower than epithelial transport-related factor curve values (1.35%/min vs 2.2%/min), but were identical with the clearance rates of the sum of both factors plus factor background. Factor analysis allows quantitative assessment of epithelial transport without interference of other clearance mechanisms and should be evaluated further in different pulmonary disorders.

Aerosols↗
PubMed1980

Using BMDP and SPSS for a Q factor analysis.

While Euclidean distances and Q factor analysis may sometimes be preferred to correlation coefficients and cluster analysis for developing a typology, commercially available software does not always facilitate their use. Commands are provided for using BMDP and SPSS in a Q factor analysis with Euclidean distances.

Computers↗
PubMed1989

Factor analysis of dynamic structures (FADS) in the diagnosis of renal disease.

Factor analysis of dynamic structures (FADS) has been used in the interpretation of dynamic scintigraphic studies since the technique was described by Bazin et al. (1980). This study was designed to analyse to what extent, if any, does physiological factor analysis of dynamic renal data really help the clinician and by how much the method improves the diagnostic accuracy when compared to deconvolution analysis and parenchymal transit time (PTT) measurements. One hundred and fifty patients who were clinically, biochemically and radiologically investigated for renal disease were included in the study. Fifty of these were found to have no clinical evidence of renal disease, 50 were diagnosed as having non obstructive kidney disease and 50 had evidence of renal obstruction. Data obtained from 99mTc-DTPA renography were processed using deconvolution (with PTTs) and physiological factor analysis and the results compared by ROC analysis. Clinically the information gained from factor analysis was superior to that obtained from deconvolution with PTT measurements in that a more accurate differentiation between an obstructive nephropathy and an obstructive uropathy was obtained. It is considered that physiological factor analysis enhanced the clinical information obtained from renography, increases diagnostic accuracy and obviates the need for diuresis renography.

Humans↗
PubMed1989

Determination of left ventricular wall motility injury by factor analysis in patients with advanced ischemic heart disease.

Left ventricular phase and amplitude images (Fourier analysis, PAI) and factor analysis images (FAI) from gated radionuclide ventriculography were obtained in 235 patients after myocardial infarction (MI) and in 44 patients with well documented ischemic heart disease (IHD) in order to assess areas of regional left ventricular motility injury (LVMI). The sensitivity of FAI for LVMI detection was higher than with PAI (36.3% vs 22.7% in patients without MI; 76.6% vs 68% in those after anterior MI; and 53.2% vs 31.9% after posterior MI, respectively). In 2.9% of all patients PAI were unclear due to small time activity amplitudes and heart rate irregularity, whereas FAI could be easily assessed. Significantly decreased left ventricular ejection fraction was observed predominantly after anterior MI in connection with distinct signs of LVMI in a large area of anterior wall or in the anteroseptal and/or apical region. Areas of LVMI could be sharply delineated in FAI; however, in contrast to PAI, FAI is unable to distinguish between dyskinetic and akinetic regions. The use of both PAI and FAI is recommended for more detailed detection of regional LVMI in patients with IHD.

Coronary Disease↗
PubMed1994

[Evaluation of renal function by factor analysis using 99mTc-MAG3].

The kinetics of 99mTc-mercapto-acetyltriglycine (MAG3), a new renal scintigraphic agent, was studied by factor analysis in patients with chronic renal disorders, and its application to assessment of the renal function was evaluated. Data were collected for 30 minutes from immediately after intravenous injection of MAG3 at 370 MBq, the first pass image and serial renal scintigrams were obtained, and factor analysis was attempted simultaneously. Since most of MAG3 is excreted via the kidney during the first pass, factor analysis was performed. Two factors reflecting renal parenchymal components and pelvic components could be separated in 8 (Cre < or = 2.9 mg/dl) of 10 patients, and they corresponded with respective segmental renograms. In the remaining 2 (Cre > or = 3.0 mg/dl), separation was impossible by 2-factor analysis, and 3-factor analysis was needed. Factor analysis is considered to allow objective evaluation of renal function without setting the ROI.

Adult↗
PubMed1993

Factor analysis and computerized EEG: preliminary data on schizophrenic patients.

Factor Analysis can extract salient features from EEG data and reduce redundancy of multi-channel computerized EEG data. A 16-channel computerized frequency analysis of background brain electrical activity during 3 functional conditions (eyes closed, eyes open and hyperventilation) was carried out in two groups, fifty healthy subjects and twenty-three schizophrenics. The power log-transformed relative values of normal subjects and schizophrenic patients were submitted to Factor Analysis and the resulting factor scores were compared. Schizophrenics showed EEG abnormalities in delta 2, theta 1 and alpha 2 bands for the first factor, accounting for the eyes closed condition, and in theta 2 and beta 2 bands for the second factor, accounting for the eyes open condition. This preliminary study demonstrates the utility of Factor Analysis in managing and comparing computerized EEG data.

Adult↗
PubMed2002

Factor analysis of Gulf War illness: what does it add to our understanding of possible health effects of deployment?

The authors conducted factor analysis on survey data from 1,779 Persian Gulf War veterans. Their purposes were to: 1) determine whether factor analysis identified a unique "Gulf War syndrome" among veterans potentially exposed to chemical warfare agents; 2) compare the findings of factor analysis with those from an epidemiologic analysis of symptom prevalence; and 3) observe the behavior of factor analysis when performed on dichotomous data. The factor analysis identified three factors, but they were not unique to any particular deployment group. A unique pattern of illness was not found for the larger group of veterans potentially exposed to chemical warfare agents; however, veterans who had witnessed the demolition of chemical warfare agents at the Khamisiyah site in Iraq had a greater prevalence of dysesthesia. An analysis of the performance of dichotomous variables in factor analysis showed that the standard criteria used to determine the number of relevant factors and the dominant variables within them may be inappropriate. While Gulf War veterans appear to suffer an increased burden of illness, there is insufficient evidence to identify a unique syndrome in this population of deployed servicemen and women. Furthermore, the results provide evidence that factor analysis may make a limited contribution in this area of research.

Adult↗
PubMed1990

Factor analysis of in vitro antitumor activities of platinum complexes.

Factor analysis was applied to the data matrix of in vitro growth inhibitory activities of 52 platinum complexes against 9 tumor cell lines, L1210, P388, Lewis lung, AH66, AH66F, HeLa S3, KB, HT-1197 and HT-1376 cell lines. Three factors were obtained by the principal factor analysis method. After the varimax rotation of these three factors, tumor cell lines were classified into four groups according to their factor loadings. The platinum complexes were characterized by the factor scores. Cisplatin was situated in an extreme position as compared with the other platinum complexes. In vivo antitumor activities of the platinum complexes were tested against L1210 and LL murine tumor models. The in vivo activity against L1210 showed a negative correlation with that against LL. Factor 2 scores of the complexes obtained by factor analysis of in vitro antitumor activities showed a good correlation with these in vivo antitumor activities. Then, the structure-factor 2 score relationships among platinum complexes were analyzed by the Free-Wilson method. From this analysis, structure-activity relationships for carrier ligands and leaving groups are proposed. Factor analysis is suggested to be a useful method to establish an efficient screening system for platinum complexes.

Animals↗
PubMed1982

Professional performance among dental students: a factor analysis.

This study uses factor analysis of dental school performance to extract the underlying factors that are inherent in a set of a student's grades and to evaluate whether a given grade may be associated with more than one factor. Results suggest that overall performance is associated with factors that may be identified as basic science, dental science, and manual skill. The dental science factor appears to be developed during professional training and tends to be less clearly defined that the basic science and manual skills factors, respectively, the associations of clinical course grades with the defined factors are generally low, reflecting the complex involvement of dental clinic performance. It is reasonable to speculate, therefore, that dental school grades, when compounded together as overall GPA across the basic abilities of the students, constitute a likely source of variation that accounts for difficulties in prediction studies when they are used as criterion variables.

Clinical Competence↗