Faculty Bibliography

A mathematical model is presented for measurements that include substantial fluctuation and error. Under the assumptions that the fluctuation-error variance is the same for all subjects, and that the distributions of fluctuation-error variance within subjects and "true" values of the measurements in the population are normal, Bayes' theorem produces a simple estimate of the "true" value of a measurement, and a standard error, conditional on a single observation. The model is easily extended to several observations. Methods for estimating the parameters of the model from a data set are presented, and applied to diastolic blood pressures of patients in the authors' primary care clinic. The test-retest reliability of a single blood pressure measurement for this population is 0.41. Because continuous measurements are often dichotomized into "normal" and "abnormal" ranges by a threshold criterion, the authors present formulas for the positive predictive value when a decision rule based on a given number of observations is used in a population with respect to a threshold criterion for the "true" values. For example, classifying their patients as hypertensive on the basis of the average of two readings exceeding 90 mm Hg diastolic pressure would have a positive predictive value of 52% for the "gold standard" of average diastolic pressure exceeding 90 mm Hg. Formulas to calculate the frequency with which patients will be classified "abnormal" by one decision rule but will be classified "normal" by later application of another rule are provided and used to "predict" the frequency with which this crossover phenomenon should have occurred in the enrollment phase of the Hypertension Detection and Follow-up Programs.(ABSTRACT TRUNCATED AT 250 WORDS)

To evaluate caring for the poor and uninsured in divisions of general medicine (DGMs), and to document the impact of recent reimbursement changes on division ambulatory care activity, the authors conducted a survey of DGM directors. Questionnaires mailed to directors of 214 divisions or residency programs yielded 120 responses. DGMs staffed, on average, three ambulatory sites, with a median of 17,000 visits per site. Overall, 66% of visits were by poor, underinsured, and uninsured patients. The majority of directors (75%) considered care of the poor a goal of their divisions. The most commonly reported response to the cost containment environment was implementation of revenue-generating measures (66%); 19% reported reductions in care to the poor; and 20% reported increased service to this group. It is concluded that DGMs care for large numbers of poor and uninsured patients and therefore must carefully evaluate the impacts of current policy proposals on their future ambulatory care activities.

A projection operator technique is used to derive an equation for local tissue tracer content Q(t), assuming linear multicompartmental kinetics for tracer utilization. The resulting equation has the form (Equation: see text), where F and Ca(t) denote local blood flow and concentration of tracer, respectively. Tissue complexity is contained within the new parameters lambda, xi(t), and psi(t), where the time-dependent coefficients are expressed as sums of exponentials. Two simple applications are considered: tissue heterogeneity and internal trapping of tracer. The relationship to effective single compartmental analysis, as is used for local cerebral blow flow determination, is evaluated.

The radiation absorbed dose for nine neck lesions distributed among four thyroid-cancer patients was measured directly from images taken after administration of a treatment dose of 131I. The tumor volume was measured with anterior plus lateral pinhole images by determining magnification and assuming an ellipsoidal shape. Uptake and effective half-life were determined from serial anterior images by use of a calibration curve. Dose lower limits ranged from 2,400 to 29,900 rad. Response to treatment was judged on the basis of one or more follow-up scans at least 8 mo later. All lesions responded to the therapy administration which ranged from 150 to 175 mCi.

In cysteamine-induced duodenal ulcer, an animal model for the clinical disease, lesions are characteristically produced on the anterior and posterior walls of the proximal duodenum. Using this model, we investigated factors that may affect duodenal ulcer localization and intensity. Mobilization of the gastroduodenum by severing its ligaments; circumscribed application of acetic acid to the serosa of the lateral wall of the duodenum; or placement of materials (e.g., gelfoam, parafilm) on the proximal duodenum, each decreased the intensity of anterior-posterior ulcers and resulted in formation of atypical, mostly distal duodenal ulcers. The effect of these manipulations on acid secretion suggests that their influence on the development of duodenal ulcer is not entirely due to modulation of gastric secretion. The data indicate that the localization of induced duodenal ulcer can be shifted distally and is therefore not site specific. This study provides new clues and techniques for the study of the pathogenesis of duodenal ulcer disease.

Neutralization of acid was evaluated in rat proximal duodenal segments isolated from biliary and pancreatic secretions. Duodenal ulcerogenic doses of cysteamine produced a significant decrease in acid disposal 0.5-2 hr after treatment. Oral or subcutaneous administration of the duodenal ulcerogen was effective. The potent ulcerogen cysteamine produced a more pronounced decrease than propionitrile (a weak duodenal ulcerogen). The failure of ethanolamine, a nonulcerogenic structural analog of cysteamine to significantly alter acid disposal suggests that the effect is not due to the toxic properties of the duodenal ulcerogen. The results reinforce the concept that the duodenum is able to dispose of significant quantities of acid. The decrease in acid-handling may contribute to duodenal susceptibility to acid after treatment with ulcerogens and possibly reflects pathophysiologic changes early in duodenal ulceration.