Comparison of exercise test scores and physician estimation in determining disease probability.

BACKGROUND: The recent American College of Cardiology/American Heart Association exercise testing guidelines provided equations to calculate treadmill scores and recommended their use to improve the predictive accuracy of the standard exercise test. However, if physicians can estimate the probability of coronary artery disease as well as the scores can, there would be no reason to add this complexity to test interpretation. To compare the exercise test scores with physician's estimation of disease probability, we used clinical, exercise test, and coronary angiographic data to compute the recommended scores and print patient summaries and treadmill reports. OBJECTIVE: To determine whether exercise test scores can be as effective as expert cardiologists in diagnosing coronary disease. METHODS: Five hundred ninety-nine consecutive male patients without previous myocardial infarction with a mean +/- SD age of 59 +/- 11 years were considered for this analysis. With angiographic disease defined as any coronary lumen occlusion of 50% or more, 58% had disease. The clinical/treadmill test reports were sent to expert cardiologists and to 2 other groups, including randomly selected cardiologists and internists, who classified the patients as having high, low, or intermediate probability of disease and estimated a numerical probability from 0% to 100%. RESULTS: Forty-five expert cardiologists returned estimates on 336 patients, 37 randomly chosen practicing cardiologists returned estimates on 129 patients, 29 randomly chosen practicing internists returned estimates on 106 patients, 13 academic cardiologists returned estimates on 102 patients, and 27 academic internists returned estimates on 174 patients. When probability estimates were compared, the scores were superior to all physician groups (0.76 area under the receiver operating characteristic curve to 0.70 for experts [P=.046], 0.73 to 0.58 for cardiologists [P=.003], and 0.76 to 0.61 for internists [P=.006]). Using a probability cut point of greater than 70% for abnormal, predictive accuracy was 69% for scores compared with 64% for experts, 63% to 62% for cardiologists, and 70% to 57% for internists. CONCLUSION: Although most similar to the disease estimates of the presence of clinically significant angiographic coronary artery disease provided by the expert cardiologists, the scores outperformed the nonexpert physicians.

Deja vu: nosocomial hepatitis B virus transmission and fingerstick monitoring.

PURPOSE: Three patients with acute hepatitis B virus infection were identified who had been hospitalized on the same medical ward during a 19-day period several months earlier. An investigation was undertaken to determine if nosocomial transmission had occurred. SUBJECTS AND METHODS: A cohort study of patients admitted to the medical ward during the 19-day period in 1995 was conducted. In addition, we reviewed medical charts and laboratory records of all patients with acute hepatitis B virus infection who had been admitted to the hospital from 1992 through October 1996 to identify other cases with possible nosocomial acquisition. RESULTS: The 3 patients who had developed acute hepatitis B infection 2 to 5 months after hospitalization on the same medical ward had diabetes mellitus but no identified risk factors for hepatitis B infection. A source patient with diabetes mellitus and hepatitis B "e" antigenemia also was present on the same medical ward at the same time; all 4 patients were infected with the same viral subtype (adw2). Diabetes mellitus and fingerstick monitoring were associated with illness (P <0.001). Through the review of medical charts and laboratory records, 11 additional cases of suspected nosocomial acquisition via fingersticks were identified in 1996, including two clusters involving an unusual subtype of hepatitis B virus (adw4). The fingerstick device employed had a reusable base onto which disposable lancet caps were inserted. There was ample opportunity for cross-contamination among patients because deficiencies in infection control practices, particularly failure to change gloves between patients, were reported by nurses and patients with diabetes mellitus. CONCLUSION: Transmission during fingerstick procedures was the most likely cause of these cases of nosocomial hepatitis B infection. Contamination probably occurred when healthcare workers failed to change gloves between patients undergoing fingerstick monitoring, although other means of contamination cannot be ruled out.

A consensus approach to diagnosing coronary artery disease based on clinical and exercise test data.

OBJECTIVE: To demonstrate that a consensus approach for combining prediction equations based on clinical and exercise test variables derived from different populations can stratify patients referred for possible coronary artery disease (CAD) into low-, intermediate-, and high-risk groups. DESIGN: Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible CAD. After derivation of a logistic equation in our own training set of patients, this equation, along with two other equations developed independently by other investigators, was validated in a test set. The validation strategy for the consensus approach included the following: (1) calculation of probability scores for each patient using each logistic equation independently; (2) determination of probability thresholds in the training set to divide the patients into three groups-low risk (prevalence CAD <5%), intermediate risk (5 to 70%), and high risk (>70% prevalence of CAD); (3) using agreement among at least two of three of the prediction equations to generate "consensus" for each patient; and (4) application of the consensus approach thresholds to the test set of patients. SETTINGS: Two university-affiliated Veteran's Affairs medical centers. PATIENTS: We studied 718 consecutive men between 1985 and 1995 who had coronary angiography within 3 months of an exercise treadmill test for suspected CAD. The population was randomly divided into a training set of 429 patients and a test set of 289 patients. Patients with previous myocardial infarction or coronary artery bypass surgery, valvular heart disease, left bundle branch block, or any Q waves present on their resting ECG were excluded from the study. MEASUREMENTS: Recording of clinical and exercise test data along with visual interpretation of the ECG recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports. RESULTS: We demonstrated that by using simple clinical and exercise test variables, we could improve on the standard use of ECG criteria during exercise testing for diagnosing CAD. Using the consensus approach divided the test set into populations with low, intermediate, and high risk for CAD. Since the patients in the intermediate group would be sent for further testing and would eventually be correctly classified, the sensitivity of the consensus approach is 94% and the specificity is 92%. The consensus approach controls for varying disease prevalence, missing data, inconsistency in variable definition, and varying angiographic criterion for stenosis severity. The percent of correct diagnoses increased from the 67% for standard exercise ECG analysis and from the 80% for multivariable predictive equations alone to >90% correct diagnoses for the consensus approach. CONCLUSIONS: The consensus approach has made population-specific logistic regression equations portable to other populations. Excellent diagnostic characteristics can be obtained using simple data and measurements. The consensus approach is best applied utilizing a programmable calculator or a computer program to simplify the process of calculating the probability of CAD using the three equations.

Manipulation of a hospital antimicrobial formulary to control an outbreak of vancomycin-resistant enterococci.

Infection control practices are not uniformly successful in limiting outbreaks of vancomycin-resistant enterococci (VRE). Despite the implementation of barrier precautions for VRE-infected patients, nearly one-half of the inpatients at our center were found to have gastrointestinal colonization by VRE. In an attempt to control the outbreak, we altered the antibiotic formulary by restricting the use of cefotaxime and vancomycin and adding beta-lactamase inhibitors to replace third-generation cephalosporins. The use of clindamycin was also restricted because of a concomitant outbreak of Clostridium difficile colitis. After 6 months, the average monthly use of cefotaxime, ceftazidime, vancomycin, and clindamycin had decreased by 84%, 55%, 34%, and 80%, respectively (P < .02). The point prevalence of fecal colonization with VRE decreased from 47% to 15% (P < .001), and the number of patients whose clinical specimens were culture positive also gradually decreased. A change in antibiotic use appears to have significantly affected our VRE outbreak when previous measures failed.

Experience with a hospital-wide outbreak of vancomycin-resistant enterococci.

BACKGROUND: Vancomycin-resistant enterococci (VRE) were first detected in our institution in 1991. An outbreak was recognized in late 1992 when there was a sudden rise in the number of patients per month with VRE. Little information exists concerning the natural history of infection with these pathogens, and the effect of antimicrobial therapy is unclear. Recent guidelines emphasize prudent use of vancomycin and prompt institution of barrier precautions to limit the spread of vancomycin resistance. METHODS: Data were obtained by review of microbiologic and clinical records. Patients were categorized according to site of infection, and outcome of therapy was assessed. Hospital antibiotic usage was analyzed to determine any correlation with the outbreak. Infection control measures instituted in 1993 included patient isolation, environmental cleaning, and a reemphasis of barrier precautions. Surveillance cultures were performed to assess the extent of the outbreak in January 1995. RESULTS: VRE were detected in clinical cultures from 159 patients from 1991 through 1994. Mortality rate was 48%, but in most cases death could not be attributed to enterococcal infection. Patients with wound infections healed without specific therapy. Many patients with bacteremia had resolution with ampicillin or without specific therapy. Patients were widely scattered throughout the hospital from the beginning of the outbreak. Hospital usage of cefotaxime correlated with the number of cases. Infection control measures were not successful. Surveillance culture results in January 1995 revealed that 53% of all medical and surgical inpatients had fecal colonization with VRE. Genetic analysis of selected isolates revealed that one strain predominated, but at least seven distinct strains were identified. CONCLUSIONS: Our data suggest that many infections with VRE resolve without specific therapy. The infection control measures we used were ineffective, possibly because of the multiple strains present in our hospital. Isolation of all patients with VRE is impractical when there is widespread fecal carriage.

Prediction of atherosclerotic cardiovascular death in men using a prognostic score.

Treadmill and clinical data were gathered prospectively on consecutive patients who underwent exercise testing for evaluation for coronary artery disease in a 1,200 bed Veterans Affairs Medical Center. From 3,609 men referred for exercise testing from 1984 to 1990, 3,134 patients remained after excluding those with significant valvular heart disease and those with prior coronary artery bypass surgery. Of these, 588 were selected for clinical reasons to undergo cardiac catheterization within 3 months of evaluation leaving 2,546 who were not selected. Over 3 years, there were 158 cardiovascular deaths, 99 nonfatal myocardial infarcts and 183 patients who underwent coronary artery bypass surgery. In the total population, the Cox proportional-hazards model demonstrated the following characteristics to be statistically significant independent predictors of time until cardiovascular death: a history of congestive heart failure and/or taking digoxin, exercise-induced ST depression, the change in systolic blood pressure during exercise, and exercise capacity in METs. Using the Cox model coefficients to weight the variables, a simple score (the Veterans Affairs Prognostic Score) was constructed based on these items. Average annual cardiovascular mortality was plotted against the score enabling its estimation for any given patient. In the subgroup selected for cardiac catheterization (n = 588), the mean score was greater, consistent with a poorer prognosis, compared with the total population; 53% (n = 312) had a score < -2 associated with an annual mortality < 2%. Thus, in over half of the patients selected for catheterization, the catheterization was unnecessary if performed to lessen their chance of cardiovascular death, since no intervention could improve their prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Typing of serum-soluble HLA-B27 antigen by ELISA.

An ELISA using serum as soluble HLA antigen source was developed for HLA-B27 typing. Two sandwich assays were run in parallel. The first assay utilized a monoclonal antibody (mAb) reacting with a determinant expressed by both HLA-B7 and B27 antigens; the other assay utilized a mAb reactive with HLA-B7 antigens but not with HLA-B27 antigens. After incubation with serum samples, bound HLA antigen was detected using an anti-beta 2m antibody conjugated to peroxidase and a chromogenic substrate. Absorbance of each well was measured at 490 nm. Based on analysis of absorbances obtained with panels of specimens of known HLA phenotypes, a mathematical algorithm was developed to derive the specimen HLA-B27 phenotype from its ELISA absorbance values. Despite the lack of monospecific mAb, an accurate HLA-B27 typing was possible. 362 specimens (including 151 HLA-B27-positive) were tested. Agreement between microlymphocytotoxicity and ELISA was 99.2%. No correlation between the level of HLA-B27 antigen reactivity and the amount of total HLA class I antigen in serum was observed. This report demonstrates the possibility of using serum-soluble HLA antigen and ELISA technology for histocompatibility testing. The assay offers several significant advantages over microlymphocytotoxicity: no need for cell preparation, batch testing capabilities and objective, reproducible interpretation of results.

Noninvasive assessment of changes in myocardial perfusion and ventricular performance following exercise training.

Seventeen coronary patients (CAD) underwent thallium (TI-201) treadmill and radionuclide (RNV) ejection fraction supine bicycle testing before and after 5.6 +/- 1.6 (mean +/- SD) months of an exercise program. Thallium data were assessed both using analog images and a computerized circumferential profile technique. Patients exercised on the treadmill to a higher workload after the exercise program, but achieved a similar pressure-rate product. When interpreting the analog thallium images, only 50% agreement was obtained for the assessment of changes in myocardial perfusion (pre/post-training). The computer technique, however, had low inter-intraobserver variability (6%) and better agreement (90.5%). Using the circumferential profile method, five patients improved (a total of 11 regions) and one patient worsened (with two regions). Before the exercise program, the ejection fraction (EF) response to supine bike exercise was normal (an increase greater than 11%) in four, flat in seven, and severely abnormal (a decrease of more than 4%) in six patients. After the exercise program, even though achieving similar or higher pressure-rate products, six patients improved their EF response, nine did not change, and two worsened. Of the five patients who improved their thallium images, one improved his EF response, two remained normal, and two did not change. One patient worsened both his thallium study and the EF response after the exercise program. Changes in thallium exercise images and the EF response to supine exercise occurred in our patients after an exercise program, but were not always concordant. Indeed, of five patients with exercise-induced ischemic ST changes before and after training, the EF response improved in three whereas myocardial perfusion was unchanged. Reasons for this lack of agreement are discussed, and have been considered in the planning of a randomized trial of the effects of an exercise program on myocardial perfusion and function.

Radionuclide perfusion images before and after cardiac rehabilitation.

Improvement in cardiac perfusion has not been demonstrated in man to explain the increased functional capacity secondary to exercise training. Thallium imaging is a noninvasive method of evaluating myocardial perfusion and scaring. Therefore, using thallium exercise tests, we studied 17 patients with coronary heart disease before and after a mean of 6 months participation in cardiac rehabilitation program emphasizing exercise training. Interobserver variability in imaging interpretation was considered by reading images blinded both individually and in consensus. Agreement with defects called by consensus occurred at least 51% of the time individually and normal readings agreed at least 90% of the time. By consensus reading, seven patients showed improved perfusion, seven showed no change, and three worsened following training. Our study shows that thallium scans may be used to demonstrate central changes in myocardial perfusion after cardiac rehabilitation, but larger controlled studies considering redistribution and utilizing image enhancement are necessary to see if such changes are truly secondary to this intervention.