Biomedical subjects

L Joseph

Publications and source records attributed to L Joseph.

171 records · Page 10Linked to original sources

PubMedDate not supplied

Who needs an exercise stress test? Evaluating the new American College of Sports Medicine risk stratification guidelines.

PURPOSE: The American College of Sports Medicine recently published new guidelines to classify individuals at increased risk for coronary heart disease (CHD) before starting a vigorous (> 60% maximum oxygen consumption) exercise program. We compared the prognostic value of the new guidelines to the earlier guidelines. METHODS: Subjects included men and women over 30 years of age, free from known CHD according to the Lipid Research Clinic Follow-up Cohort. Endpoints included an abnormal exercise test result (+/- 1 mm ST, anginal chest pain, or exercise hypotension) and future death of CHD ascertained during an average 12.2 years of follow-up. Data analysis included 2 x 2 contingency tables to compare the test characteristics of the old and new guidelines. RESULTS: Among 4,074 subjects, 219 (5.4%) had abnormal exercise test results and 65 (1.6%) eventually died of CHD. The new guidelines classified 75.7% of individuals as high risk versus 58.7% using the old guidelines. Comparing the new guidelines with the old, test sensitivity was significantly (P = 0.007) higher for patients with an abnormal exercise test result (87% versus 77%) than for patients who died of CHD (100% versus 99%). Test specificity of the new guidelines was significantly (P < 0.001) lower than the old guidelines for individuals with abnormal exercise test results (25% versus 42%) and those who died of CHD (25% versus 42%). The new guidelines also showed significantly lower overall diagnostic accuracy and positive likelihood ratios compared with the old guidelines for both patients with abnormal exercise test results and those who died of CHD. The positive predictive value for the new and old guidelines for both patients with abnormal exercise test results and those who died of CHD were similar. CONCLUSIONS: Although the new guidelines are more sensitive in the abnormal exercise test result endpoint, they are less specific and overall less accurate than the old guidelines given the low prevalence of CHD in this asymptomatic population. The current guidelines should be modified to better target high-risk adults.

Adult↗

PubMedDate not supplied

Inferences for likelihood ratios in the absence of a "gold standard".

Likelihood ratios are extensively used to evaluate the performances of diagnostic tests and to update prior odds of disease to posttest odds. Since few tests are truly 100% accurate, including many used as "gold standards," it is important to be able to estimate likelihood ratios in cases where no such standard is available. In this paper, methods to calculate point and interval estimates for likelihood ratios are described. The results numerically coincide with those reviewed by Centor when a "gold standard" is assumed available, but typically provide wider interval estimates when such a standard is not available, reflecting the increased uncertainty inherent in such situations. Unlike previous techniques, the methods do not require normal approximations or logarithmic transformations, and hence provide accurate estimates even when parameter distributions are highly skewed. The methods are illustrated using the results of two different diagnostic tests for the presence of an intestinal parasitic infection.

Algorithms↗

PubMedDate not supplied

A comparison of parametric and nonparametric approaches to ROC analysis of quantitative diagnostic tests.

Receiver operating characteristic (ROC) analysis, which yields indices of accuracy such as the area under the curve (AUC), is increasingly being used to evaluate the performances of diagnostic tests that produce results on continuous scales. Both parametric and nonparametric ROC approaches are available to assess the discriminant capacity of such tests, but there are no clear guidelines as to the merits of each, particularly with non-binormal data. Investigators may worry that when data are non-Gaussian, estimates of diagnostic accuracy based on a binormal model may be distorted. The authors conducted a Monte Carlo simulation study to compare the bias and sampling variability in the estimates of the AUCs derived from parametric and nonparametric procedures. Each approach was assessed in data sets generated from various configurations of pairs of overlapping distributions; these included the binormal model and non-binormal pairs of distributions where one or both pair members were mixtures of Gaussian (MG) distributions with different degrees of departures from binormality. The biases in the estimates of the AUCs were found to be very small for both parametric and nonparametric procedures. The two approaches yielded very close estimates of the AUCs and the corresponding sampling variability even when data were generated from non-binormal models. Thus, for a wide range of distributions, concern about bias or imprecision of the estimates of the AUC should not be a major factor in choosing between the nonparametric and parametric approaches.

Bias↗

PubMedDate not supplied

Conventional and chained standard gambles in the assessment of coronary heart disease prevention and treatment. Canadian Collaborative Cardiac Assessment Group.

The authors compared the abilities of descriptive and valuational health-related quality-of-life measures to discriminate healthy participants (n=39) from those on diets for dyslipidemia (n=35) and angina patients (n=30). On the rating scale, the time tradeoff, and the General Health Perception subscale of the SF-36 Health Survey, the participants with dyslipidemia or angina reported lower mean scores than the healthy participants. No differences were detected between these groups on conventional or chained standard gamble (SG) scales. The distribution of the conventional and the chained SG scores was very skewed, with the vast majority of scores being equal or very close to the maximum score. It is concluded that in this study the discriminant ability of the chained SG was comparable to that of the conventional SG and inferior to descriptive and non-risky valuational scaling techniques. This may be explained by the distortion of probabilities, by a misunderstanding of the SG chained assessment, and by a strong certainty effect.

Adult↗

PubMedDate not supplied

Medical decision making in the choice of a thrombolytic agent for acute myocardial infarction. Quebec Acute Coronary Care Working Group.

Little is known about how physicians make decisions when the evidence is incomplete or controversial. While thrombolysis improves survival following acute myocardial infarction (AMI), conflicting evidence exists as to any specific agent's superiority, particularly if cost-effectiveness is considered. Using a Bayesian hierarchical model, the authors examined the patient, physician, and hospital characteristics that are related to the decision-making process concerning the choice of thrombolytic agent in a prospective registry of 1,165 AMI patients receiving thrombolysis. Tissue plasminogen activator (t-PA) was administered to 432 patients (31.8%) and streptokinase (SK) to the remainder. The presence of an anterior infarction, a previous myocardial infarction, low blood pressure, a cardiologist decision maker, younger age, and receiving treatment within six hours after the start of symptoms were independent predictors of receiving t-PA. The levels of importance that physicians accorded to these patient characteristics differed according to their practicing institutions. Generally, they followed evidence-based medicine and reasonably targeted high-risk patients to receive the more expensive t-PA. However, they also preferentially treated younger patients, where only a small absolute advantage appears to exist.

Aged↗

PubMedDate not supplied

The hepatitis B immunization strategy in Nova Scotia: is it effective?

Since 1987, both hepatitis B disease and hepatitis B vaccine utilization have increased dramatically in Nova Scotia. We present a review of hepatitis B vaccine utilization relative to the occurrence of disease in Nova Scotia. In the two regions with the highest incidence rates, cases have been increasingly associated with lifestyle-related risk factors. Vaccine utilization was primarily for occupational risks. The current provincial hepatitis B immunization strategy is to recommend immunization to targeted high-risk groups. This strategy was judged to be ineffective. The cost of the vaccine is the most important deterrent for adopting an expanded or universal immunization strategy. The pooling of hepatitis B vaccine orders across Canada is suggested as a means to effect significant reductions in the cost of vaccine. Provincial programs would then be able to expand coverage to include populations at immediate risk and youngsters prior to the start of high-risk activity.

Communicable Disease Control↗

PubMedDate not supplied

An epidemic of hepatitis B among injection drug users in a rural area.

An epidemic of hepatitis B occurring in a rural area of Nova Scotia in 1988 and 1989 was investigated. This epidemic identified injection drug use (IDU) as the major determinant of transmission and was the first highly visible indication of IDU in rural Nova Scotia. Contact-tracing was used to identify 186 injection drug users (IDUs), of whom 153 (82%) were interviewed. Of 133 (72%) IDUs who underwent serological testing, 78 had serological evidence of hepatitis B infection. Using epidemiological criteria, 57 IDUs formed a cluster of hepatitis B infections. Using logistic regression techniques, age (O.R. = 1.1), the total number of IDU-contacts named (O.R. = 1.1), and the number of hepatitis B seropositive IDU-contacts named (O.R. = 1.3), were identified as risk factors predictive of an IDU being a cluster case. The characterization of this epidemic may be useful as a model for the spread of hepatitis B and other viral infections among IDUs in rural areas.

Adolescent↗

PubMedDate not supplied

Panel discussion.

Explore the source record for details and available documents.

Congresses as Topic↗

PubMedDate not supplied

[Reasons for the hospitalization and length of stay of a homeless population in Montreal].

OBJECTIVE: To compare the hospitalization experience of a homeless population with that of the residents of a low socioeconomic area. METHODS: The homeless hospitalization records (n = 245) were compared with the records of the 3,553 residents of the Département de Santé Communautaire of Saint-Luc Hospital territory who were admitted to the same hospital. RESULTS: The homeless population is mainly composed of young men. Mental health diagnoses are more frequent while cardiovascular and the obstetrical diagnoses are more rarely seen. Homelessness is associated with an 11.2 increased risk of organic psychosis, a 6.1 risk increase of functional psychosis and a 3.8 risk increase of personality disorders, neurosis and substance abuse. Obstetrical diagnoses are 20 times less frequent among homeless women while the cardiovascular risk did not seem to be affected in our sample. The lengths of stay are similar.

Adolescent↗