Biomedical subjects

Michael Proschan

Publications and source records attributed to Michael Proschan.

5 recordsLinked to original sources

PubMed2003

Estimating the probability of toxicity at the target dose following an up-and-down design.

One of the most important aspects of a phase I trial or other acute toxicity study is estimating accurately the probability of toxicity that is associated with the recommended dose. We use the biased coin up-and-down design to allocate and isotonic regression to estimate toxicity probabilities and determine the recommended dose. We then derive, using bootstrap methods, an estimate of the probability of toxicity at the recommended dose. Small sample properties of this estimator are also evaluated. Published in 2003 by John Wiley & Sons, Ltd.

Bias↗

PubMed2003

Multiple outputation: inference for complex clustered data by averaging analyses from independent data.

This article applies a simple method for settings where one has clustered data, but statistical methods are only available for independent data. We assume the statistical method provides us with a normally distributed estimate, theta, and an estimate of its variance sigma. We randomly select a data point from each cluster and apply our statistical method to this independent data. We repeat this multiple times, and use the average of the associated theta's as our estimate. An estimate of the variance is given by the average of the sigma2's minus the sample variance of the theta's. We call this procedure multiple outputation, as all "excess" data within each cluster is thrown out multiple times. Hoffman, Sen, and Weinberg (2001, Biometrika 88, 1121-1134) introduced this approach for generalized linear models when the cluster size is related to outcome. In this article, we demonstrate the broad applicability of the approach. Applications to angular data, p-values, vector parameters, Bayesian inference, genetics data, and random cluster sizes are discussed. In addition, asymptotic normality of estimates based on all possible outputations, as well as a finite number of outputations, is proven given weak conditions. Multiple outputation provides a simple and broadly applicable method for analyzing clustered data. It is especially suited to settings where methods for clustered data are impractical, but can also be applied generally as a quick and simple tool.

Acute Disease↗

PubMed2002

Effects of hormone replacement therapy and antioxidant vitamin supplements on coronary atherosclerosis in postmenopausal women: a randomized controlled trial.

CONTEXT: Hormone replacement therapy (HRT) and antioxidant vitamins are widely used for secondary prevention in postmenopausal women with coronary disease, but no clinical trials have demonstrated benefit to support their use. OBJECTIVE: To determine whether HRT or antioxidant vitamin supplements, alone or in combination, influence the progression of coronary artery disease in postmenopausal women, as measured by serial quantitative coronary angiography. DESIGN, SETTING, AND PATIENTS: The Women's Angiographic Vitamin and Estrogen (WAVE) Trial, a randomized, double-blind trial of 423 postmenopausal women with at least one 15% to 75% coronary stenosis at baseline coronary angiography. The trial was conducted from July 1997 to January 2002 in 7 clinical centers in the United States and Canada. INTERVENTIONS: Patients were randomly assigned in a 2 x 2 factorial design to receive either 0.625 mg/d of conjugated equine estrogen (plus 2.5 mg/d of medroxyprogesterone acetate for women who had not had a hysterectomy), or matching placebo, and 400 IU of vitamin E twice daily plus 500 mg of vitamin C twice daily, or placebo. MAIN OUTCOME MEASURE: Annualized mean (SD) change in minimum lumen diameter (MLD) from baseline to concluding angiogram of all qualifying coronary lesions averaged for each patient. Patients with intercurrent death or myocardial infarction (MI) were imputed the worst rank of angiographic outcome. RESULTS: The mean (SD) interval between angiograms was 2.8 (0.9) years. Coronary progression, measured in mean (SD) change, worsened with HRT by 0.047 (0.15) mm/y and by 0.024 (0.15) mm/y with HRT placebo (P =.17); and for antioxidant vitamins by 0.044 (0.15) mm/y and with vitamin placebo by 0.028 (0.15) mm/y (P =.32). When patients with intercurrent death or MI were included, the primary outcome showed an increased risk for women in the active HRT group (P =.045), and suggested an increased risk in the active vitamin group (P =.09). Fourteen patients died in the HRT group and 8 in the HRT placebo group (hazard ratio [HR], 1.8; 95% confidence interval [CI], 0.75-4.3), and 16 in the vitamin group and 6 in the vitamin placebo group (HR, 2.8; 95% CI, 1.1-7.2). Death, nonfatal MI, or stroke occurred in 26 HRT patients vs 15 HRT controls (HR, 1.9; 95% CI, 0.97-3.6) and in 26 vitamin patients and 18 vitamin controls (HR, 1.5; 95% CI, 0.80-2.9). There was no interaction between the 2 treatment interventions. CONCLUSION: In postmenopausal women with coronary disease, neither HRT nor antioxidant vitamin supplements provide cardiovascular benefit. Instead, a potential for harm was suggested with each treatment.

Aged↗

PubMed2002

Women's angiographic vitamin and estrogen trial: design and methods.

The Women's Angiographic Vitamin and Estrogen trial was a randomized, double-blind, placebo-controlled study designed to test the efficacy of estrogen replacement and antioxidant vitamins for preventing angiographic progression of coronary artery disease. Postmenopausal women with one or more angiographically documented coronary stenoses of 15-75% at baseline were assigned in a 2 x 2 factorial randomization to active hormone replacement therapy (conjugated estrogens for women who had had a hysterectomy or conjugated estrogens with medroxyprogesterone for women with intact uteri) or placebo and to active vitamins E and C or their placebos. Seven clinical centers, five in the United States and two in Canada, randomized 423 women between July 1997 and July 1999. Quantitative coronary angiography was performed at baseline and repeated after projected mean follow-up of 3 years.

Antioxidants↗

PubMed2001

Baseline Characteristics of Participants in the Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT).

-Diuretics and ss-blockers have been shown to reduce the risk of cardiovascular morbidity and mortality in people with hypertension in long-term clinical trials. No study has compared newer more costly antihypertensive agents (calcium antagonists, ACE inhibitors, and alpha-adrenergic blockers) with diuretics for reducing the incidence of cardiovascular disease in an ethnically diverse group of middle-aged and elderly hypertensive patients. The study is a randomized, double-blind, active-controlled clinical trial designed to determine whether the incidence of the primary outcome, fatal coronary heart disease or nonfatal myocardial infarction, differs between treatment initiation with a diuretic versus each of 3 other antihypertensive drugs. Men and women aged >/=55 years with at least 1 other cardiovascular disease risk factor were randomly assigned to chlorthalidone (12.5 to 25 mg/d), amlodipine (2.5 to 10 mg/d), lisinopril (10 to 40 mg/d), or doxazosin (2 to 8 mg/d) for planned follow-up of 4 to 8 years. This report describes the baseline characteristics of the Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) participants. A total of 42 448 participants were randomized from 625 sites in the United States, Canada, Puerto Rico, and the US Virgin Islands. The mean age was 67 years, with 35% aged >/=70 years. Among those randomized, 36% were black, 19% were Hispanic, and 47% were women. The sample includes a high proportion of people with diabetes (36%), patients with existing cardiovascular disease (47%), and smokers (22%). There were no important differences between the randomized treatment groups at baseline. ALLHAT will add greatly to our understanding of the management of hypertension by providing an answer to the following question: are newer antihypertensive agents similar, superior, or inferior to traditional treatment with diuretics?

Journal Article↗