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PubMed2002

Predictors of course completion for the U.S. Army pharmacy specialist course.

The purpose of this study was to determine predictors of successful completion of the U.S. Army Medical Department pharmacy specialist (91Q) training program. The sample consisted of 143 students from four course iterations, and only students enrolled in the course for the first time were included for analysis. The relationship between 16 predictor variables and successful completion was assessed. Five variables, the ranks of private (E1) and specialist (E4), cross-trainee status, gender, and Armed Services Vocational Aptitude Battery (ASVAB) general technical (GT) score, were found to be significant predictors using simple linear regression. Using hierarchical multiple linear regression analysis, three variables, service component, gender, and ASVAB GT score, were found to have a significant unique shared variance with success. The results of this study indicate that ASVAB GT scores are predictive of success (p < 0.01) in the 91Q training program. Using these predictors, the selection process may be modified to improve the likelihood of student success in the course.

Accreditation↗

PubMed2003

Health related quality of life in women with elderly onset rheumatoid arthritis.

OBJECTIVE: To examine the association of elderly onset rheumatoid arthritis (RA) with health related quality of life in a population based cohort of older women. METHODS: A nested case-control study of elderly onset RA within the Iowa Women's Health Study (IWHS), a prospective cohort established in 1986 of 41,000 women aged 55 to 69 years. A supplemental questionnaire was mailed to 122 RA cases and 1132 frequency matched controls from the cohort. We used unconditional logistic regression and linear regression to examine the association of elderly onset RA with self-reported measures of functional disability and quality of life. RESULTS: Elderly onset RA was associated with a 6-fold risk (OR 6.0, 95% CI 3.6-10.1) of significant functional disability (Health Assessment Questionnaire score (3) 1). Similarly, elderly onset RA was significantly associated with lower physical component scores of the Medical Outcome Study Short Form-12 (37.2 +/- 10.9 vs 43.6 +/- 11.6; p < 0.001). CONCLUSION: Among a community based cohort, elderly onset RA was strongly associated with functional disability and reduced quality of life. These associations were independent of other age associated factors including depression, recent fracture, and multiple comorbidities.

Age of Onset↗

PubMed2005

Influences of health insurance status on clinical treatments and outcomes for 4,714 patients after acute myocardial infarction in 14 Chinese general hospitals.

BACKGROUND: It is unknown whether insurance status influences care provided and patients' prognosis, in China. METHODS: This retrospective cohort study included medical records of 4,714 patients with acute myocardial infarction aged 20 and older, discharged consecutively from 14 Chinese hospitals between January 2000 and February 2003. Uni-variate analysis, multivariate logistic regression and linear regression were used to compare differences in patients' characteristics, care provided and prognosis between insured patients and the uninsured. RESULTS: The uninsured were more likely to be older, female, have transfer admissions, and less likely to be hospitalized to institutions with cardiac interventional facilities, intensive care units or coronary care units. The uninsured were also less likely to undergo diagnostic procedures, interventions and to receive medications, and stayed shorter in hospital and consumed less health care resources. In-hospital mortality in the uninsured, the non-government insured and the government insured was 10.5%, 12.2% and 8.4% respectively. After adjusting for potential confounders, odd ratio in hospital mortality was 1.079 (95% CI, 0.836-1.392) and 0.763 (95% CI, 0.559-1.041) for the non-government insured and the government insured, compared to the uninsured. At significant level of 0.05, we could not assert insurance status is a significant factor to in-hospital mortality.

Adult↗

PubMed2005

Thymidine analogue mutation profiles: factors associated with acquiring specific profiles and their impact on the virological response to therapy.

BACKGROUND: Studies have suggested that HIV-1 may develop thymidine analogue mutations (TAMs) by one of two distinct pathways - the TAM1 pathway (including mutations 41L, 210W and 215Y) or the TAM2 pathway (including mutations 67N, 70R and 219E/Q) - under the pressure of a not fully suppressive thymidine-analogue-containing regimen. METHODS: Frozen plasma samples stored in the EuroSIDA repository were selected and sent to two central laboratories for genotypic analysis. We considered 733 patients with at least one genotypic test showing > or =1 TAMs (the first of these tests in chronological order was used). TAM1 and TAM2 genotypic profiles were defined in accordance with previous literature. Statistical modelling involved logistic regression and linear regression analysis for censored data. RESULTS: The observed frequencies of patterns classifiable as TAM1 or TAM2 profiles were markedly higher than the probabilities of falling into these classifications by chance alone. The chance of detecting a TAM2 profile increased by 25% per additional year of exposure to zidovudine. We found that mutations 67N and 184V were not associated with a particular TAM profile. In the presence of TAM2 profiles, the adjusted mean difference in the 6-month viral reduction was 0.96 log10 copies/ml (95% confidence interval: 0.20; 1.73) higher in patients who started stavudine-containing regimens instead of zidovudine-containing regimens. CONCLUSIONS: This study provides evidence that the suggested TAM clustering is a real phenomenon and that it may be driven by which thymidine analogue the patients has used. In patients with TAM2-resistant viruses, stavudine appears to retain greater viral activity than zidovudine.

Anti-HIV Agents↗

PubMed1981

M-response quantification: a technique.

Median nerve responses in 13 patients and 9 normal subjects were evaluated using surface bipolar stimulation. The M response from surface electrodes placed upon the thenar eminence was recorded on a fiberoptic chart recorder and simultaneously subjected to true electronic integration. Comparison between the integrated M response and the M index (the product of the M response peak-to-peak amplitude and total duration) revealed a highly correlated linear regression. This linear relationship was present when stimulating both at the wrist (r2 = 0.96) and the antecubital fossa (r2 = 0.95). Statistically significant differences were observed between the integrated M response of 5 normal adult men and men with carpal tunnel syndrome (n 3, p less than 0.01) or anterior horn cell or neuropathic processes (n 4, p less than 0.001). Differences of borderline significance were noted between normal women (n = 4) and women with carpal tunnel syndrome (n 4, p less than 0.05) or anterior horn cell or neuropathic processes (n 2, p less than 0.01). There was no correlation between the integrated M response and the distal latency in patients with carpal tunnel syndrome. It is concluded that the M index is a highly reliable method of quantifying the M response as an approximation of integration in median nerve studies, but that this measurement holds little relationship with the presence of the distal neuropathic processes studied.

Adult↗

PubMedDate not supplied

A statistical estimator of the spatial distribution of the water-table altitude.

An algorithm was designed to statistically estimate the areal distribution of water-table altitude. The altitude of the water table was bounded below by the minimum water-table surface and above by the land surface. Using lake elevations and stream stages, and interpolating between lakes and streams, the minimum water-table surface was generated. A multiple linear regression among the minimum water-table altitude, the differerence between land-surface and minimum water-table altitudes, and the water-level measurements from surficial aquifier system wells resulted in a consistently high correlation for all groups of physiographic regions in Florida. A simple linear regression between land-surface and water-level measurements resulted in a root-mean-square residual of 4.23 m, with residuals ranging from -8.78 to 41.54 m. A simple linear regression between the minimum water table and the water-level measurements resulted in a root-mean-square residual of 1.45 m, with residuals ranging from -7.39 to 4.10 m. The application of the multiple linear regression presented herein resulted in a root-mean-square residual of 1.05 m, with residuals ranging from -5.24 to 5.63 m. Results from complete and partial F tests rejected the hypothesis of eliminating any of the regressors in the multiple linear regression presented in this study.

Algorithms↗

PubMed1985

The ventilatory response to carbon dioxide. An analysis of data obtained by the rebreathing method.

The ventilatory response to carbon dioxide using the rebreathing method was studied repeatedly in four healthy volunteers. The data were collected and processed in different ways using a microcomputer. Least squares linear regression analysis described the responses almost as accurately as a non-linear second-order polynomial regression. Linear regression analysis was undertaken on VI/PE'CO2 points, first breath-by-breath and then on three different groupings of breaths. The gradients and intercepts obtained by grouping agreed with those from breath-by-breath analysis both for a single response and for the mean result of a number of responses. Grouping tended to increase the correlation coefficient of a response, but widened the statistical confidence limits of the calculated gradient. The performance variability between repeated responses, the same no matter which data points were used, produced a range of gradients for each subject which was larger than the confidence limits on the gradient of a single response.

Adult↗

PubMed1990

Use of nonlinear regression to analyze enzyme kinetic data: application to situations of substrate contamination and background subtraction.

In a recent publication, A. Lundin, P. Arner, and J. Hellmér [Anal. Biochem. 177, 125-131 (1989)] describe a method whereby kinetic substrate assays can be performed when the assay mixture includes a significant contaminating levels of substrate. Their method requires various rearrangements of the data, and involves three separate linear regression calculations. We show how the same data may be analyzed directly, and far more simply, by nonlinear regression. Unlike the linear regression method, nonlinear regression allows direct calculation of the actual values for Km, Vmax, and the concentration of contaminating substrate (as well as estimates of their standard errors); the former method gives only apparent values. The nonlinear regression technique is also statistically a more valid means of analysis, as the rearrangements required to give linearized equations will considerably distort the error distribution and render simple unweighted linear regression inappropriate. The ease of incorporating extra parameters into standard equations when nonlinear regression is used is further illustrated by fitting enzyme reaction data which describe a first-order process when a significant nonspecific background is present. For this equation no simple rearranged linear plot is possible, but nonlinear regression is easily applied to determine the kinetic parameters.

Enzymes↗

PubMed2005

Relationship between perceived exertion and mean power frequency of the EMG signal from the upper trapezius muscle during isometric shoulder elevation.

The aim of the study was to investigate the relationship between a fatigue-induced increase of perceived exertion in the neck with a decrease of mean power frequency (MPF) in the surface electromyography (sEMG) signal during repeated shoulder elevation endurance tasks. About Thirty-two healthy women (age range 20-62) performed two maximum 6-min shoulder elevation endurance tasks at 30% of their maximal voluntary contraction (MVC) level, separated by a rest of 6 min. During these exercises, perceived exertion was estimated using the Borg scale (range 0-10), whereas the MPF of the sEMG signal from the upper trapezius was simultaneously detected. Linear regression analysis was applied over time for each trial and subject for both MPF and Borg scale rating values. The MPF was normalized by the intercept of the linear regression analysis. The resulting slopes of normalized mean power frequency (nMPF) and Borg scale rating were correlated with each other by linear regression for both trials. In order to investigate the individual behavior of fatigue effects between trials, Delta (trial 2-trial 1) slopes of nMPF and Borg scale ratings were calculated for each subject. These slopes of nMPF and Borg scale ratings were correlated with each other as well by linear regression. The increase of Borg scale ratings, as well as the decrease of nMPF, were significantly higher in trial 2 than trial 1 (P<0.01). The results show a linear correlation between slopes of nMPF and Borg scale ratings for both trials 1 and 2 (r=0.76, P<0.01). Trial-to-trial slopes (Delta (trial 2-trial 1)) of nMPF and Borg scale rating, were also significantly correlated (r=0.68, P<0.05). Thus, the individually sensed increase of perceived exertion in the neck during trial 2 was accompanied by a simultaneously higher detected decrease of nMPF. These findings indicate a close relationship between subjective perception of exertion in the neck and objectively assessed muscle fatigue of the upper trapezius.

Adult↗

PubMedDate not supplied

Ultrasound biomicroscopy dark room provocative testing: a quantitative method for estimating anterior chamber angle width.

PURPOSE: To describe a quantitative method for measuring the iridocorneal angle recess area, and, using this, to evaluate factors associated with appositional angle-closure during dark room provocative testing using ultrasound biomicroscopy (UBM). METHODS: All patients (178 patients, 178 eyes) with clinically narrow angles referred for UBM dark room provocative testing between September 1996 and March 1998 were enrolled in this study. Images of the inferior quadrant of the angle taken under standardized dark and light conditions were analyzed. The angle recess area (ARA) was defined as the triangular area demarcated by the anterior iris surface, corneal endothelium, and a line perpendicular to the corneal endothelium drawn from a point 750 microm anterior to the scleral spur to the iris surface. ARA, and acceleration and gamma-intercept of the linear regression analysis of the ARA were calculated. In the linear regression formula, y = ax + b, the acceleration a describes the rate at which the angle widens from the scleral spur; the y-intercept b describes the distance from the scleral spur to the iris. RESULTS: Under dark conditions, the angles in 99 patients (55.6%) showed evidence of appositional angle-closure during testing. ARA (0.11 +/- 0.04 vs. 0.15 +/- 0.05 mm2, P < .0001, Student t-test), acceleration a (0.22 +/- 0.15 vs. 0.26 +/- 0.17, P = .068), and y-intercept b (66 +/- 46 vs. 92 +/- 47 microm, P = .0003) were smaller in eyes that were occluded. In the eyes that were not occluded, y-intercept b showed no significant difference between light and dark conditions (P = .1, paired t-test), while acceleration a did (P < .0001). In the eyes that were occluded, both decreased significantly under dark conditions (P < .0001). CONCLUSIONS The ARA linear regression formula provides useful quantitative information about angle recess anatomy. The more posterior the iris insertion on the ciliary face, the less likely the provocative test will be positive.

Adult↗

PubMed1998

Identification of early glaucoma cases with the scanning laser ophthalmoscope.

PURPOSE: This study aimed to define the confocal laser scanning ophthalmoscope (Heidelberg Retina Tomograph [HRT]) parameters that best separate patients with early glaucoma from normal subjects. STUDY DESIGN: A cross-sectional study. PARTICIPANTS: A total of 80 normal subjects and 51 patients with early glaucoma participated (average visual field mean deviation = -3.6 dB). INTERVENTION: Imaging of the optic nerve head with the HRT and analysis using software version 1.11 were performed. MAIN OUTCOME MEASURES: The relation between neuroretinal rim area and optic disc area, and cup-disc area ratio and optic disc area, was defined by linear regression of data derived from the normal subjects. The normal ranges for these two parameters were defined by the 99% prediction intervals of the linear regression between the parameter and optic disc area, for the whole disc, and for each of the predefined segments. Normal subjects and patients were labeled as abnormal if the parameter for either the whole disc or any of the predefined segments was outside the normal range. The sensitivity and specificity values of the method were calculated. RESULTS: The highest specificity (96.3%) and sensitivity (84.3%) values to separate normal subjects and those patients with early glaucoma were obtained using the 99% prediction interval from the linear regression between the optic disc area and the log of the neuroretinal rim area. Similar specificity (97.5%) and lower sensitivity (74.5%) values were obtained with the 99% prediction interval derived from regression between the disc area and cup-disc area ratios. Poor separation between groups was obtained with the other parameters. CONCLUSIONS: The HRT, using the technique of linear regression to account for the relationship between optic disc size and rim area or cup-disc area ratio, provides good separation between control subjects and patients with early glaucoma in this population.

Aged↗

PubMed1996

Adjusted variable plots for Cox's proportional hazards regression model.

Adjusted variable plots are useful in linear regression for outlier detection and for qualitative evaluation of the fit of a model. In this paper, we extend adjusted variable plots to Cox's proportional hazards model for possibly censored survival data. We propose three different plots: a risk level adjusted variable (RLAV) plot in which each observation in each risk set appears, a subject level adjusted variable (SLAV) plot in which each subject is represented by one point, and an event level adjusted variable (ELAV) plot in which the entire risk set at each failure event is represented by a single point. The latter two plots are derived from the RLAV by combining multiple points. In each point, the regression coefficient and standard error from a Cox proportional hazards regression is obtained by a simple linear regression through the origin fit to the coordinates of the pictured points. The plots are illustrated with a reanalysis of a dataset of 65 patients with multiple myeloma.

Biometry↗

PubMed2003

Two-step multivariate adaptive regression splines for modeling a quantitative relationship between gas chromatography retention indices and molecular descriptors.

The relationship between retention indices and molecular descriptors of alkanes is established by two-step multivariate adaptive regression splines (TMARS). TMARS combines linear regression with multivariate adaptive regression splines (MARS). It is demonstrated for the present data set that using linear regression or MARS modeling alone causes lack of fit. TMARS avoids lack of fit and appreciably improves the prediction ability for the model. The use of this combined approach permits the development of additional understanding of the adaptive nature in MARS modeling.

Chromatography, Gas↗

PubMed2005

Assessing hemlock decline using visible and near-infrared spectroscopy: indices comparison and algorithm development.

Near-infrared reflectance spectroscopy was evaluated for its effectiveness at predicting pre-visual decline in eastern hemlock trees. An ASD FieldSpec Pro FR field spectroradiometer measuring 2100 contiguous 1-nm-wide channels from 350 nm to 2500 nm was used to collect spectra from fresh hemlock foliage. Full spectrum partial least squares (PLS) regression equations and reduced stepwise linear regression equations were compared. The best decline predictive model was a 6-term linear regression equation (R2= 0.71, RMSE = 0.591) based on: Carter Miller Stress Index (R694/R760), Derivative Chlorophyll Index (FD705/FD723), Normalized Difference Vegetation Index ((R800 - R680)/(R800 + R680)), R950, R1922, and FD1388. Accuracy assessment showed that this equation predicted an 11-class decline rating with a 1-class tolerance accuracy of 96% and differentiated healthy trees from those in very early decline with 72% accuracy. These results indicate that narrow-band sensors could be developed to detect very early stages of hemlock decline, before visual symptoms are apparent. This capability would enable land managers to identify early hemlock woolly adelgid infestations and monitor forest health over large areas of the landscape.

Algorithms↗

PubMed1997

On the linearization of eruption series of the permanent teeth.

In order to confirm the linearization of permanent eruption, Masuyama's linearization method was applied to the data of Kitamura's study. At first, we considered the eruption age t alpha i of permanent teeth T alpha, where alpha corresponds a tooth of every description, and examined the linear regression of Y alpha i = log10 t alpha i on m(y) alpha (the mean of Y alpha i with respect to i), but the result was not good. For the correlation coefficient r between two variables in linear regression, the percentage of subjects with r > or = 0.970 was only 10.3% in males and 28.8% in females in Kitamura's study. Next we took notice of the eruption age u beta i of each tooth, which is the beta-th in order of eruption. The fitness of the linear regression of Z beta i = log10 u beta i on mz beta (the mean of Z beta i) was very good. The percentage of subjects with r > or = 0.970 increased to 80.0% in males and 86.0% in females. Then we used m(y) (beta) (rearranged m(y) alpha in order of increasing size) instead of mz beta as an independent variable in the linear regression. The degree of the linearization was slightly inferior to that using mz beta. In every linearization, a quasi-fixed point with coordinates (C, C) existed on the linearized dentition plot, where the value of C was almost equal in each way, i.e., C = 10.23 (years) for males and C = 8.91 (years) for females in Kitamura's data. This linearized dentition plot will be useful in detecting certain growth disturbances. The existence of a quasi-fixed point may be useful in forecasting the age of the eruption of subsequent teeth, once the first eruption is observed.

Aging↗

PubMed1983

Diurnal variation for inhibition of eating by bombesin in the rat.

Sprague-Dawley male albino rats ate sweet milk at the midpoint of the day or night phase of a 12:12 light/dark cycle 1 min after IP 0.9% NaCl or synthetic bombesin (BBS; 2-32 micrograms/kg) following 24-hr food deprivation. Exogenous BBS inhibited food intake in a dose-related manner during the day; a linear regression line accounted for 85% of the total variance for percentage suppression of food intake by BBS in 30 min. In contrast, inhibition of eating by BBS at night was not dose-related; a linear regression line accounted for only 16% of the variance. Rats were tested under identical conditions following 3-hr food deprivation. Exogenous BBS (4-64 micrograms/kg) inhibited food intake in a dose-related manner at night; a linear regression line accounted for 92% of the total variance. In contrast, inhibition of eating by BBS during the day was not as orderly; a linear regression line accounted for only 44% of the variance. The 8 micrograms/kg dose was twice as potent for inhibition of eating of 25% GIBCO 116EC liquid diet than it was for inhibition of eating sweet milk at the midpoint of the day phase. These results describe diurnal variation in potency of exogenous BBS for inhibition of food intake in the rat. Whether BBS is more or less potent at night than during the day depends upon the particular dose, degree of hunger of the rat, and probably the type of food being eaten.

Animals↗

PubMed1999

Progression of defects in the central 10-degree visual field of patients with retinitis pigmentosa and choroideremia.

PURPOSE: To determine the progression of defects in the central 10-degree visual field in patients with retinitis pigmentosa and choroideremia by means of univariate linear regression with respect to the mean deviation. METHODS: In a retrospective study, results of automated static perimetry in the central 10-degree visual field were reviewed for patients with retinitis pigmentosa and choroideremia. Univariate linear regression of mean deviation was undertaken for each eye that had field data from at least five tests in addition to the prior static perimetric experience during a period of 3.5 years or more. Data from 30 eyes of 16 patients fulfilled eligibility requirements; the mean number of fields was 5.8 (range, five to 10) and the mean follow-up period was 64 months (range, 42 to 97 months). Eyes were classified as progressive if the regression coefficient was negative and significantly different from zero, with a P value of less than .05. RESULTS: Among 14 patients in whom both eyes were eligible for univariate linear regression analysis, a statistically significant progression was demonstrated in both eyes in four patients, only in one eye in five patients, and in neither eye in five patients. One of two patients, in whom only one eye was eligible for the study, showed significant progression in the eye. Overall, 14 (47%) of 30 eyes showed statistically significant progression with respect to the mean deviation. No eye showed significant improvement. CONCLUSIONS: Automated static perimetry of the central 10-degree visual field measured approximately once or twice a year demonstrated the progressive nature of the disease with the use of univariate linear regression of mean deviation in 47% of eyes with retinitis pigmentosa and choroideremia during the follow-up period of 3.5 years or more. These results may be useful in understanding the clinical course of the diseases and counseling patients.

Adolescent↗

PubMed1994

Use of linear multiple regression analysis on dental survey data.

The use of multiple regression analysis in dental research has increased greatly in recent years. However, in most cases insufficient or no details are given to assess the validity of the results obtained through this statistical approach. Since multiple regression is the method of choice when dealing with three or more variables, provided the assumptions are fulfilled, this study reports the use of this technique on caries data from a random sample of schoolchildren from Andalucia, Spain. Linear multiple regression was used to analyse caries experience, expressed as dmft or DMFT, a quantitative dependent variable. The explanatory or independent variables considered for each age group were gender, type of area, social class and province, following the basic survey method recommended by the World Health Organization. Laborious data transformation procedures had to be employed to comply with necessary assumptions for this statistical technique. The difficulties encountered may be partly due to the fact that all the independent variables considered in the study were categorical or qualitative variables. In the process of ensuring valid results, several helpful statistics were identified. In addition, statistically significant influences on the dependent variable studied were easily detected, as well as the order of importance of the independent variables included in the model. However, the complex data transformation procedures required to validate assumptions in this study suggested that in some instances it could prove extremely difficult to use linear multiple regression on survey data.

Adolescent↗