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T R Church

Publications and source records attributed to T R Church.

25 records · Page 2Linked to original sources
PubMed1993

Estimating the duration of ongoing prevention trials.

The authors present a method of estimating the duration of ongoing prevention trials, showing how the method was applied to the Colon Cancer Control Study, a University of Minnesota study of occult blood testing undertaken to screen for colorectal cancer in older Minnesotans. In that study, begun in 1975 and ongoing, as in several other recent large prevention trials, it was necessary, after the start of the study, to revise upward the initial estimates of study duration derived from general population experience. The underestimates arose because the planners had not adequately taken various population selection factors into account in estimating the expected number of events in the control group. In this paper, the authors outline a method for estimating control group event rates and study duration requirements (and, in some circumstances, also sample size requirements) of prevention studies, via models of disease-specific and all-cause standardized mortality ratios which adjust for various selection effects. The authors also validate the model for disease-specific standardized mortality ratios by means of independent estimates of disease incidence and case survival.

Aged↗
PubMed1989

Sensitivity, specificity, and positive predictivity of the Hemoccult test in screening for colorectal cancers. The University of Minnesota's Colon Cancer Control Study.

Data are presented on the sensitivity, specificity, and positive predictivity of the Hemoccult test based on the experience of the Minnesota Colon Cancer Control Study, a randomized clinical trial to determine whether the use of the Hemoccult test can reduce mortality from colorectal cancer. Rehydrating the slides with a drop of water before processing resulted in an increase in positivity (2.4% to 9.8%), and sensitivity (80.8% to 92.2%) but a decrease in specificity (97.7% to 90.4%) and positive predictivity (5.6% to 2.2%). The effects of age and sex were also evaluated. The test was less specific for men than women (p = 0.03). Specificity was highest for those less than 60 yr of age and decreased with increasing age (p = 0.05). The positive predictivity increased with age from 1.6% for those under 60 yr to 3.6% for those over 70 yr (p = 0.0004).

Age Factors↗
PubMed1982

Effects of theophylline on breathlessness and exercise tolerance in patients with chronic airflow obstruction.

Theophylline is commonly prescribed for patients with nonasthmatic chronic airflow obstruction (CAO) even though clinical efficacy is not well established. We studied objective and subjective responses to theophylline in 14 men with CAO. Subjects randomly received week-long treatments of placebo or theophylline at two dosages: one that produced low (8.7-13.0 micrograms/ml) and the other high (16.0-23.6 micrograms/ml plasma concentrations. During the final three days of each treatment, we measured spirometric and hemodynamic function. Exercise tolerance was assessed with the 12 minute walk and progressive cycle ergometry. The patients' perception of breathlessness during the usual activities of daily living was evaluated with the oxygen cost diagram and the breathlessness rating. For low and high dose theophylline there were significant (p less than .05) increases in forced vital capacity (7.1 +/- 2.1 percent; 12.0 +/- 1.7 percent), forced expiratory volume at one second (14.6 +/- 4.9 percent; 12.1 +/- 3.3 percent) and in pulse rate (8.3 +/- 1.2 percent; 19.1 +/- 3.1 percent), but no changes in blood pressure. There were also no significant differences among the three treatments for any of the tests which assessed exercise tolerance or breathlessness. These results suggest that most patients with CAO experience little symptomatic benefit from taking theophylline.

Adult↗
PubMed1980

Efficacy of theophylline in "irreversible" airflow obstruction.

We studied ventilatory, hemodynamic, and subjective responses to different plasma theophylline concentrations in 10 patients with "irreversible" airflow obstruction. Subjects received theophylline at doses that produced low (9.0 to 12.5 micrograms/mL) and high (17 to 22 micrograms/mL) peak plasma concentrations; subjects also received placebo. A significant (P less than 0.05) dose-related difference in pulmonary function was observed between each treatment. The mean maximal increase in forced expiratory volume at 1 second over placebo was 21.3% for high-dose theophylline and 6.0% for low dose. Both treatments were well tolerated with respect to hemodynamic changes and other adverse effects. Despite improved findings in pulmonary function tests patients were unable to distinguish either treatment from placebo in terms of improvement in breathlessness.

Aged↗
PubMedDate not supplied

A school-based strategy to assess children's environmental exposures and related health effects in economically disadvantaged urban neighborhoods.

The School Health Initiative: Environment, Learning, Disease (SHIELD) study is a novel school-based investigation of children's environmental health in economically disadvantaged urban neighborhoods of Minneapolis. This article describes the study design and summarizes lessons learned about recruiting and monitoring this historically understudied population. The SHIELD study focused on measuring children's exposures to multiple environmental stressors [volatile organic chemicals (VOCs), environmental tobacco smoke, allergens, bioaerosols, metals, pesticides, polychlorinated biphenyls (PCB), phthalates] and exploring related effects on respiratory health (e.g., lung function) and learning outcomes (e.g., standardized test scores, academic achievement). It involved intensive exposure monitoring, including environmental measurements inside and outside the children's schools and inside their homes, personal measurements with passive dosimeters worn by the children, and biological marker measurements in blood and urine. The SHIELD participants comprised a stratified random sample of 153 "index" children and 51 of their siblings enrolled in grades 2-5 at two adjacent elementary schools. The Minneapolis Public Schools (MPS) assisted with identifying, contacting, recruiting, and monitoring this population, which traditionally is difficult to study because families/children are highly mobile, speak a diversity of languages, frequently do not have a telephone, endure economic hardships, often do not trust researchers, and have a spectrum of unconventional lifestyles and living arrangements. Using a school-based approach, the overall SHIELD enrollment (response) rate was 56.7%, with a wide disparity between English-speaking (41.7%) and non-English-speaking (71.0%) families/children. Most children remained involved in the study through both monitoring sessions and exhibited an acceptable degree of compliance with study protocols, including providing blood and urine samples. Results indicate that it is both practical and affordable to conduct probability-based exposure studies in this population, but that it is also important to improve our understanding of factors (e.g., cultural, economic, psychological, social) affecting the willingness of families/children to participate in such studies, with special emphasis on developing cost-effective recruitment methods.

Air Pollution, Indoor↗