A Bayesian model for longitudinal count data with non-ignorable dropout

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73907/1/j.1467-9876.2008.00628.x.pd

Prospective Evaluation of Two Dosing Equations for Theophylline in Premature Infants

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90141/1/j.1875-9114.1996.tb02995.x.pd

Accuracy and Reliability of Dosing Equations to Individualize Theophylline Treatment of Apnea of Prematurity

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90103/1/j.1875-9114.1995.tb04360.x.pd

Evaluation of Conventional and New Maximum Heart Rate Prediction Models for Individuals

In October of 1992 I submitted an abstract to the American College of Sports Medicine, co-authored with Dr. Schork and Dr. Edington from the University of Michigan, to present our study at the 1993 Annual Meeting. A few weeks later I received Volume 24, issue 10 of Medicine and Science in Sports and Exercise, where Whaley and colleagues had published a similar paper. Discouraged by the bad timing, I never tried to publish my own paper. Several years later, other similar papers have been published, arguing for a correction to the conventional 220-age formula for maximum heart rate. I realized I should have tried to publish my paper back in 1993! I have dug out the original poster presentation materials, scanned them, and prepared this document for the sake of teaching my students (who often quote Tanaka et al. and Gellish et al.) the importance of prompt publication of their work.The purpose of this study was to develop a regression model to predict maximum heart rate (HRmax) from basic sociodemographic variables and to compare it with the 220-age rule of thumb. Data were obtained from 635 adults of all ages, gender, and physical activity levels, rigorously tested for maximum aerobic capacity. HRmax was found to be significantly correlated (p<.05) to age, tobacco use in the past, current tobacco use, and self-reported physical activity. There was no evidence of a difference in HRmax between males and females (p=.997). Several significant (p<.00005) linear regression models involving these variables were developed, but their ability to explain the variation in HRmax was only slightly better than a model that relied on age alone. Based on R2 values, the age model was able to account for 44.9% of the variation in HRmax, compared to 48% when using the most complicated model. The 220-age rule of thumb also gave an r2 =.449 (44.9%), but the average estimate was biased (-8 beats per minute [b * min~l]). Individual estimates were highly inaccurate: 50.5% of the predicted values were off by 10 b * min-1 or more, compared to 27.6% with our simplest model based on age alone. Furthermore, both the 220-age rule and our regression models were very poor predictors when applied to ten-year age subgroups. It was concluded that in spite of a significant correlation between HRmax and other variables, regression models based on these variables are highly inaccurate in the prediction of individual HRmax values. Therefore, the practice of relying on them for individualized exercise prescription and as a criterion for graded exercise test termination is not warranted.UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Educación::Escuela de Educación Físic

Intraocular pressure measurement in the conscious rat

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74866/1/j.1600-0420.1999.770108.x.pd

Statistical survey of "saturation analysis" calibration curve data for prednisolone, prednisone and digoxin

An extensive survey of radioimmunoassay calibration data for prednisolone, prednisone and digoxin indicated that the common practice of preparing calibration curves with individual subject's pre-dose plasma or serum, and using this to estimate unknown concentrations for the same subject, is not supported by statistical considerations. Preparation of calibration plots from pooled data is better because this introduces less bias in estimated concentrations. Such a method also saves a great deal of time, since it is not necessary to repeat the calibration procedure each time "unknowns" are being assayed. The data suggest that there is no optimum calibration plot for all radioimmunoassays. Rather, each antibody-drug combination should be investigated thoroughly to determine the best calibration plot for the particular combination. We found that the best calibration plots are; the logistic-logarithmic plot for prednisolone; nonlinear least squares fit to a polyexponential equation for prednisone; and a weighted least squares regression of normalized % bound concentration for digoxin. The error in the radioimmunoassay is usually concentration-dependent, and, in certain regions of the standard curve, is larger than the literature indicates, since, frequently, the error has been gauged from % bound values, but should be gauged from inversely-estimated concentrations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21684/1/0000074.pd

Cushing's syndrome after treatment: Changes in cortisol and ACTH levels, and amelioration of the depressive syndrome

Twenty-three patients with pituitary adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome were studied before and after treatment. The relationship between the amelioration of the depressive syndrome and changes in cortisol and ACTH levels was investigated. There was a significant difference in mean change in 24-hour urinary free cortisol (UFC) excretion for changes in the depressed mood score from first to last visit. There were also significant correlations between decreases in UFC and decreases in both the depressed mood score and the modified Hamilton depression score. These relationships were not found for ACTH. Furthermore, with cortisol decreased to normal levels, continued high ACTH levels did not prevent improvement in depressed mood. The possibility that cortisol may also play a role in the pathogenesis and/or maintenance of the mood disorder in psychiatric patients is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25987/1/0000053.pd

A family set method for estimating heredity and stress--I : A pilot survey of blood pressure among Negroes in high and low stress areas, Detroit, 1966-1967

A pilot survey designed to test the feasibility of measuring genetic and stress variables as they relate to blood pressure levels was carried out among Negroes residing in high and low stress census tracts in Detroit, 1966-1967. Fifty-six "family sets" or 280 persons were interviewed and blood pressure recordings were taken by trained nurses. Each family set was composed of an index, a spouse, a sibling and a first cousin of index, and an unrelated person in the census tract matched to index. The method and findings of obtaining such family sets is discussed and found to be encouraging enough to initiate a larger study. It was also found that proportions of persons with hypertensive levels were significantly greater in the high stress tract (32 per cent; N = 102) than in the low stress tract (19 per cent; N = 113).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32720/1/0000088.pd

Use of Cholecystokinin to Prevent the Development of Parenteral Nutritionâ Associated Cholestasis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142290/1/jpen0100.pd