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Biomedical subjects

W J Hall

Publications and source records attributed to W J Hall.

135 records · Page 8Linked to original sources
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Monitoring and improving the content of medical residents' ambulatory care experience: a microcomputer-based method using diagnosis clusters.

Changing patterns of medical practice necessitate increased experience in ambulatory settings for internal medicine residents. Residency program directors must monitor the content and balance of the ambulatory care experience. Evaluation of ambulatory care educational programs requires a concise method of describing the illnesses seen in each outpatient setting and of monitoring individual resident activities. The authors present an easily applied, microcomputer-based method of analysis using diagnosis clusters that has been found to be useful in evaluating and modifying the ambulatory care curriculum at their institution. It provides a concise description of individual ambulatory settings, affords an opportunity to compare each setting with national norms, and identifies areas of inadequate exposure in each resident's experience.

Ambulatory Care↗
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Evaluation of early airway disease in smokers: cost effectiveness of pulmonary function testing.

We studied 73 young adults who were presently cigarette smokers to evaluate whether the identification of abnormalities in pulmonary function tests had a detectable influence on modification of smoking habits. Utilizing rate schedules for these tests presently applicable in Rochester, New York, we determined the potential cost to these subjects and community relative to the number of subjects who stopped smoking as a result of test findings. Subjects were evaluated by questionnaire and function testing including spirometry, flow-volume curves, body plethysmography and single breath nitrogen washout test (SBN2). Functional abnormalities were present in 75% of subjects screened. The SBN2 test was most sensitive, identifying 97% of subjects with any abnormality. The presence of common respiratory symptoms was found to be highly predictive of test abnormalities. Subjects were informed of results and counseled. At six-month follow-up, 7% of subjects with abnormal test results had stopped smoking. Utilizing even our most cost-effective test, the SBN2, it would cost +1,392 for each "benefit" defined as one subject not smoking for six months. Application of these screening techniques is unlikely to be effective in altering smoking habits in the absence of continued physician support.

Adult↗
PubMedDate not supplied

Persistent thallium-201 defect: can clinical, electrocardiographic and exercise hemodynamic variables predict defect normalization with reinjection?

This study was designed to assess the contribution of clinical, electrocardiographic and exercise hemodynamic variables to the prediction of normalization on resting reinjection scintigraphy of persistent thallium-201 (201Tl) myocardial perfusion defects seen with exercise and 2- to 4-hour delayed (redistribution) imaging. To evaluate this contribution, we studied 159 consecutive patients with persistent 201Tl myocardial perfusion defects on routine exercise and 2- to 4-hour-delayed scintigrams at the University of Rochester Medical Center who were classified as having moderate or greater ischemic normalization (group 1, n = 76) or minimal to no ischemic normalization (group 2, n = 83) by reinjection scintigraphy. Multiple logistic regression analysis with backward elimination was used to model the effects of clinical, electrocardiographic and exercise hemodynamic data on the odds ratio of a normalized defect. No difference was observed in the two groups with regard to gender, angina on exertion, rate-pressure product, exercise duration, resting or exertional ischemic ST changes on electrocardiogram, presence of Q waves or left ventricular hypertrophy on baseline electrocardiogram, or total number of stress thallium defects (2.8 +/- 1.5 segments). No single variable or combination of variables discriminated between groups 1 and 2 by logistic regression analysis. We conclude that defect normalization seen on resting 201Tl myocardial perfusion scintigraphy is prevalent in patients with persistent defects on routine exercise and delayed myocardial perfusion scintigraphy, and was not predictable from available clinical, electrocardiographic and exercise hemodynamic variables.

Aged↗
PubMedDate not supplied

Confidence bands for receiver operating characteristic curves.

Receiver operating characteristic (ROC) curves are mapped out by the two types of errors that are generated by varying the decision threshold used to determine which subjects will be considered abnormal. Under the conventional binormal model for the ROC curve, two-sided and one-sided simultaneous confidence bands for an entire ROC curve, or for a portion of an ROC curve, are constructed by employing Working-Hotelling-type confidence bands for simple linear regression. Pointwise confidence bands are presented for comparison. The cases in which one has only asymptotically normally distributed estimates of the parameters of the ROC curve and consistent estimates of their variance-covariance matrix are emphasized. The methods extend beyond binormal models.

Confidence Intervals↗
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Bayesian analysis of ROC curves using Markov-chain Monte Carlo methods.

The authors introduce a Bayesian approach to generalized linear regression models for rating data observed in the evaluation of a diagnostic technology. Such models were previously studied using a non-Bayesian approach. In a Bayesian analysis, the difficulties inherent in an ordinal rating scale are circumvented by using data-augmentation techniques. Posterior distributions for the regression parameters- and thereby for receiver operating characteristic (ROC) curve parameters and values, for the area under a ROC curve, differences between areas, etc.-may then be computed by Markov-chain Monte Carlo methods. Inferences are made in standard Bayesian ways. The methods are exemplified by a study of ultrasonography rating data for the detection of hepatic metastases in patients with colon or breast cancer (previously analyzed) and the results compared.

Bayes Theorem↗
PubMedDate not supplied

The accuracy of magnetic resonance imaging in patients with suspected multiple sclerosis. The Rochester-Toronto Magnetic Resonance Imaging Study Group.

OBJECTIVE: To design and implement a methodologically rigorous study to examine the accuracy of magnetic resonance imaging (MRI) in a patient population clinically suspected of having multiple sclerosis (MS). DESIGN AND SETTING: Three hundred three patients, who were referred to two university medical centers because of the suspicion of MS, underwent MRI of the head and double-dose, contrast-enhanced computed tomography (CT) of the head. The images were read by two observers individually and without knowledge of the clinical course or final diagnosis. Patients were followed up for at least 6 months and reevaluated clinically with subsequent neurological examination. Final diagnosis (MS or not MS) was made by a panel of neurologists on the basis of the clinical findings at presentation, those that developed during follow-up, and other diagnostic tests. The results of the imaging procedures were excluded to avoid incorporation bias. Diagnostic accuracy was assessed using receiver-operating characteristic analysis and likelihood ratios. RESULTS: Magnetic resonance imaging of the head was considerably more accurate than CT in diagnosing MS. The area under the receiver-operating characteristic curve for MS was 0.82 (compared with 0.52 for CT) indicating that MRI was a good but not definitively accurate test for MS. A "definite MS" reading on an MRI of the head was specific for MS (likelihood ratio, 24.9) and essentially established the diagnosis, especially in patients clinically designated as "probable MS" before testing. However, MRI of the head was negative for MS in 25% and equivocal in 40% of the patients considered to have MS by the diagnostic review committee (sensitivity, 58%). CONCLUSIONS: Magnetic resonance imaging of the head provided assistance in the diagnosis of MS when lesions were visualized. Its ability far exceeded imaging with double-contrast CT. The sensitivity and, therefore, the predictive value of a negative MRI result for MS were, however, not sufficiently high for a normal MRI to be used to conclusively exclude the diagnosis of MS.

Adolescent↗