Biomedical subjects

A S Midgette

Publications and source records attributed to A S Midgette.

7 recordsLinked to original sources

PubMed1996

Prediction of the infarct-related artery in acute myocardial infarction by a scoring system using summary ST-segment and T-wave changes.

We developed a scoring system to predict the artery responsible for an acute myocardial infarction (AMI) using ST-segment and T-wave changes on the initial electrocardiogram (ECG) using data from 228 patients (development set) with symptoms compatible with AMI and tested in a similar group of 223 patients (test set) from the Thrombolysis and Angioplasty in Myocardial Infarction (TAMI-5) Trial. Using stepwise logistic regression we were able to accurately predict the left anterior descending (LAD), right, or left circumflex (LC) coronary artery as the infarct-related artery using 2 variables: (1) the summation of the ST-segment elevation in leads V1 to V4; and (2) the summation of the T-wave negativity in leads I, aVL, and V5. In the development set, these 2 variables demonstrated respective sensitivity and specificity of 98% and 90% for LAD lesions, 82% and 85% for right narrowings, and 82% and 84% for LC narrowings. In the test set, the sensitivity and specificity were 97% and 95% for LAD lesions, 85% and 86% for right lesions, and 73% and 60% for LC coronary artery lesions. Information easily obtained on the ECG can accurately predict the likelihood of the LAD, right, or LC artery as the infarct-related artery. This may be useful in the decision to administer thrombolytic treatment.

Coronary Disease↗

PubMed1995

High-dose dexamethasone suppression testing versus inferior petrosal sinus sampling in the differential diagnosis of adrenocorticotropin-dependent Cushing's syndrome: a decision analysis.

Differentiation of adrenocorticotropin (ACTH)-dependent Cushing's syndrome between Cushing's disease and the occult ectopic ACTH syndrome is difficult. Simultaneous bilateral inferior petrosal sinus sampling (IPSS) for ACTH levels in response to corticotropin-releasing hormone has high diagnostic accuracy, but its cost-effectiveness has not been analyzed. In this study, decision analysis was used to compare two diagnostic strategies: IPSS versus high-dose dexamethasone suppression (HDD) followed by IPSS in those with a negative HDD test. Sensitivity analyses were performed for all variables. The authors found that at 100% accuracy, IPSS has an incremental cost-effectiveness ratio of $1,000,000 per life saved. Incremental cost, incremental effectiveness, and incremental cost-effectiveness are sensitive to the pretest probability of Cushing's disease, test characteristics, and test costs. As the pretest probability of Cushing's disease decreases, cost per life saved also decreases to less than 85%, the HDD strategy saves more lives and costs less. When the HDD test has a 83% sensitivity rate and a 100% specificity rate, the two strategy remains less expensive. The IPSS strategy saves lives whenever HDD specificity is less than 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

ACTH Syndrome, Ectopic↗

PubMed1993

Do cigarette smokers have diets that increase their risks of coronary heart disease and cancer?

It has been proposed that differences in diet between smokers and nonsmokers may partially explain the positive association between cigarette smoking and diseases such as cancer and coronary heart disease. To investigate the potential for this confounding, the authors studied the relation between cigarette smoking and nutrient intake in a population-based sample of 451 Australian women between 1982 and 1984. Dietary intake was determined by a quantitative food frequency questionnaire. Relations with smoking were assessed by use of analysis of covariance. The mean daily intake of total dietary fiber in current smokers was 4.1 g lower than in never smokers, with a 95% confidence interval for the difference of 1.4-6.8 g. The mean intake of total calories, cholesterol, sucrose, linoleic acid, total fat, and monounsaturated and polyunsaturated fat did not vary significantly by smoking status. However, former smokers were found to have a higher ratio of polyunsaturated to saturated fat as compared with current or never smokers and a lower intake of saturated fat as compared with current smokers. These associations persisted when the effects of total energy intake, age, years of education, and alcohol consumption were considered. The decreased ingestion of fiber by cigarette smokers could contribute to their increased risks of coronary heart disease and cancer compared with those in nonsmokers. The increased ratio of polyunsaturated to saturated fat and decreased ingestion of saturated fat in the diet of former smokers may help to reduce their risks.

Adult↗

PubMed1990

Effect of intravenous streptokinase on early mortality in patients with suspected acute myocardial infarction. A meta-analysis by anatomic location of infarction .

PURPOSE: To determine the effect of intravenous streptokinase on early mortality in patients with suspected acute anterior and acute inferior myocardial infarctions. DATA IDENTIFICATION: A literature search of English-language studies on the use of intravenous streptokinase in the treatment of suspected acute myocardial infarction for the period 1966 to 1989 using Medlars II and the bibliographies of relevant articles. In a number of instances, additional details on early mortality by location of myocardial infarction were provided by the authors. STUDY SELECTION: Of 140 originally identified articles, 6 that specifically met our inclusion criteria were selected: randomized trials that used intravenous streptokinase in a dose of 1.5 million units, with or without additional agents, compared with a group that differed only by the absence of streptokinase. Trials were selected by review of the methods section without regard for the results. DATA EXTRACTION: Data were extracted independently by two observers using specific methodologic criteria for infarct location and early mortality. After they conferred, the observers agreed completely on the data. RESULTS OF DATA SYNTHESIS: Among the 9155 patients with suspected acute anterior myocardial infarction, the mortality rate in the control group was 17.4%. In contrast, patients treated with streptokinase had a 12.5% mortality. The mean risk difference was -4.8% (95% CI, -7.5% to -2.1%) and the summary risk ratio was 0.72 (CI, 0.65 to 0.79). A total of 9650 patients with suspected inferior infarction had a mortality rate in the control group of 7.6% [corrected]. The mortality for streptokinase-treated patients was 6.6%. The mean risk difference was -0.8% (CI, -1.8% to 0.2%) and the summary risk ratio was 0.87 (CI, 0.76 to 1.01). CONCLUSIONS: Intravenous streptokinase clearly confers a protective effect against early mortality in patients with suspected acute anterior myocardial infarction. The magnitude of this effect is on the order of a 5% absolute reduction in risk of death by 21 to 35 days. For these patients, 21 need to be treated to save 1 additional life. For patients with suspected acute inferior infarction, the benefit of treatment on reducing early mortality is of smaller magnitude and less certain. These patients have an estimated absolute reduction of early mortality of approximately 1%, which would require treating 125 patients to save 1 additional life.

Humans↗

PubMed1990

Cigarette smoking and the risk of natural menopause.

We reviewed published studies on the association of age at natural menopause and cigarette smoking. All demonstrated an earlier median or mean age of menopause among smokers; for current smokers vs noncurrent smokers the difference ranged from 0.8 to 1.7 years. For studies that presented suitable data, we computed prevalence odds ratios of menopause for current smokers vs never-smokers, current smokers vs noncurrent smokers, and former smokers vs never-smokers. The Mantel-Haenzel summary odds ratios and 95% confidence intervals for these contrasts were: 1.9 (1.7-2.2), 1.7 (1.5-1.9), and 1.3 (1.0-1.7). Studies that presented data on amount of cigarettes smoked per day demonstrated "dose-response" trends when analyzed using the Mantel-Haenszel extension. The consistency of results across studies, the persistence of the effect when age and other covariates were considered, and the dose-response relation all support the hypothesis that smoking increases the risk of early menopause.

Adult↗

PubMedDate not supplied

A meta-analytic method for summarizing diagnostic test performances: receiver-operating-characteristic-summary point estimates.

The authors have devised a meta-analytic method to summarize diagnostic test performances, which they describe along with a clinical example wherein they analyze the performances of real-time ultrasonography in eight studies of the detection of proximal deep venous thrombosis of the lower extremity, selected on the basis of specific inclusion criteria. To evaluate the evidence for fitting a summary receiver operating characteristic (ROC) curve, a test of correlation between the estimates of true-positive rate (TPR) and false-positive rate (FPR) is performed. A high positive correlation argues for summarizing the studies with an ROC curve. In the absence of such correlation, a test of homogeneity is applied separately to the estimates of sensitivity (TPR) and specificity (TNR) to evaluate whether differences among studies are due to chance alone. If the estimates are homogeneous, a summary point estimate and confidence intervals (CIs) are calculated. As a final step, subgroup analyses can be performed to assess alternative explanations of variability in TPR and FPR. Within groups defined by the presence or absence of symptoms of venous thrombosis, a negative correlation between TPR and FPR and homogeneity among studies were found. For symptomatic patients, the summary TPR was 0.97 with a 95% CI of (0.94, 0.99) and the summary TNR was 0.97 (0.95, 0.99). For asymptomatic patients, the summary TPR was 0.66 (0.50, 0.81), and the summary TNR was 0.96 (0.90, 0.99). The difference in TPR between symptomatic and asymptomatic patients was statistically significant. There was no evidence that test referral bias or lack of independent interpretation of test results influenced these findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Confidence Intervals↗

PubMedDate not supplied

Cost-effectiveness of streptokinase for acute myocardial infarction: A combined meta-analysis and decision analysis of the effects of infarct location and of likelihood of infarction.

OBJECTIVE: To determine the effects of infarct location and of the likelihood of infarction on the cost-effectiveness of intravenous streptokinase (IVSK) for suspected acute myocardial infarction (AMI). DESIGN: A meta-analysis of short-term survival was combined with a simple decision tree to determine marginal cost-effectiveness ratios for different infarct locations and different likelihoods of AMI (pMI). SETTING: Six randomized trials comparing IVSK with conservative treatment. PATIENTS: 31,940 patients with onset of symptoms of AMI from four to 24 hours earlier and, with the exception of one trial, electrocardiographic abnormalities. Patients with contraindications to thrombolytic treatment such as uncontrolled hypertension were excluded. MAIN RESULTS: If AMI is certain, treatment with IVSK has marginal cost-effectiveness ratios for each additional life saved of $9,900, $56,600, and $28,400, respectively, for patients with anterior, inferior, and other locations of AMI. If pMI is 50% treatment with IVSK has marginal cost-effectiveness ratios for each additional life saved of $22,700, $131,800, and $63,100, respectively, for patients with anterior, inferior, and other locations of AMI. CONCLUSIONS: The marginal cost-effectiveness ratio for IVSK therapy of inferior infarction is six times that for anterior infarction and rises steeply as the presence of AMI becomes less certain. Assuming society is willing to pay $250,000 per life saved, IVSK therapy should be given if the chance of acute anterior infarction exceeds 7%, if the chance of inferior infarction exceeds 32%, or if the chance of infarction in other locations exceeds 17%. In patients with suspected acute myocardial infarction, IVSK saves lives and is a reasonable use of societal resources.

Boston↗