Search

Background: New tests, such as magnetic resonance imaging (MRI) and electron-beam computed tomography (CT), are being developed for the diagnosis of coronary artery disease.Objective: To determine the conditions that a new test must meet to be a cost-effective alternative to established imaging tests.Design: Decision model and cost-effectiveness analysis.Data Sources: Literature review and meta-analysis.Target Population: 55-year-old men and 65-year-old women presenting with chest pain.Time Horizon: Lifetime of the patient.Perspective: Health care policy.Interventions: MRI, electron-beam CT, exercise echocardiography, exercise single-photon emission CT, and coronary angiography.Outcome Measures: Target sensitivity and specificity values for a new noninvasive test.Results Of Base-case Analysis: Assuming that society is willing to pay $75000 per quality-adjusted life-year (QALY) gained, a new test that costs $1000 would need a sensitivity of 94% and a specificity of 90% to be cost-effective.Results Of Sensitivity Analysis: Assuming that society is willing to pay $50000 per QALY gained, a new test that costs $1000 or more would never be cost-effective. For a test that costs $500, the sensitivity and specificity must each be 95%.Conclusions: New imaging techniques, such as MRI and electron-beam CT, must be relatively inexpensive and have excellent sensitivity and specificity to be cost-effective compared with other techniques for the diagnosis of coronary artery disease. Similar analyses in other areas of health care may help to focus the development of new diagnostic technology. [ABSTRACT FROM AUTHOR]

Objective: To determine the outcome, safety, and possible cost savings of patients undergoing weekend or holiday exercise treadmill testing.Design: Medical records of all 195 patients scheduled for weekend and holiday exercise testing were reviewed, and 77.9% of patients were contacted by telephone to ascertain medical outcomes and need for further emergency department or inpatient care. Costs were calculated from estimates of days of hospitalization saved and incremental costs incurred in conjunction with weekend or holiday testing.Setting: Urban tertiary care academic medical center.Patients: A total of 195 patients were scheduled for testing, and 181 tests were performed. Over three quarters (75.1%) of patients underwent testing for assessment of chest pain. Other indications included risk stratification after myocardial infarction or coronary angioplasty or prior to noncardiac surgery, or evaluation for arrhythmias, dyspnea, or syncope.Measurements and Main Results: Outcomes included results and complications of testing, hospital course after testing, subsequent emergency department visits and readmissions, myocardial infarction, need for cardiac catheterization or revascularization, and mortality. No complications were noted during testing. In 136 patients tested for the indication of chest pain, 90 (66.2%) had negative tests, 39 (28. 7%) were intermediate, and 6 (4.4%) were positive for ischemia. Same day discharge occurred in 115 (84.6%) of the patients, saving an estimated 185 days of hospitalization ($316.83 per patient tested). Event rates over the 6 months following discharge were low.Conclusions: Weekend and holiday exercise testing is a safe and effective means of risk stratification prior to hospital discharge for patients with chest pain. It also reduces length of stay and is cost saving. [ABSTRACT FROM AUTHOR]

Context: Cardiac imaging has advanced rapidly, providing clinicians with several choices for evaluating patients with suspected coronary artery disease, but few studies compare modalities directly.Objectives: To review the contemporary literature and to compare the diagnostic performance of exercise echocardiography (ECHO) and exercise single-photon emission computed tomography (SPECT) imaging in the diagnosis of coronary artery disease.Data Sources: Studies published between January 1990 and October 1997 identified from MEDLINE search; bibliographies of reviews and original articles; and suggestions from experts in each area.Study Selection: Articles were included if they discussed exercise ECHO and/or exercise SPECT imaging with thallous chloride TI 201 (thallium) or technetium Tc 99m sestamibi for detection and/or evaluation of coronary artery disease, if data on coronary angiography were presented as the reference test, and if the absolute numbers of true-positive, false-negative, true-negative, and false-positive observations were available or derivable from the data presented. Studies performed exclusively in patients after myocardial infarction, after percutaneous transluminal coronary angioplasty, after coronary artery bypass grafting, or with recent unstable coronary syndromes were excluded.Data Extraction: Clinical variables, technical factors, and test performance were independently extracted by 2 reviewers on a standardized spreadsheet. Discrepancies were resolved by consensus.Results: Forty-four articles met inclusion criteria. In pooled data weighted by the sample size of each study, exercise ECHO had a sensitivity of 85% (95% confidence interval [CI], 83%-87%) with a specificity of 77% (95% CI, 74%-80%). Exercise SPECT yielded a similar sensitivity of 87% (95% CI, 86%-88%) but a lower specificity of 64% (95% CI, 60%-68%). In a summary receiver operating characteristic model comparing exercise ECHO performance to exercise SPECT, exercise ECHO was associated with significantly better discriminatory power (parameter estimate, 1.18; 95% CI, 0.71-1.65), when adjusted for age, publication year, and a setting including known coronary artery disease for SPECT studies. In models comparing the discriminatory abilities of exercise ECHO and exercise SPECT vs exercise testing without imaging, both ECHO and SPECT performed significantly better than exercise testing. The incremental improvement in performance was greater for ECHO (3.43; 95% CI, 2.74-4.11) than for SPECT (1.49; 95% CI, 0.91-2.08).Conclusions: Exercise ECHO and exercise SPECT have similar sensitivities for the detection of coronary artery disease, but exercise ECHO has better specificity and, therefore, higher overall discriminatory capabilities as used in contemporary practice. [ABSTRACT FROM AUTHOR]

Background: Cardiac involvement is common in acute Lyme disease, and case reports suggest that cardiac abnormalities might also occur years after the primary infection.Objective: To determine the prevalence of cardiac abnormalities in persons with previously treated Lyme disease.Design: Population-based, retrospective cohort study with controls.Setting: Nantucket Island, Massachusetts.Participants: From among 3703 adult respondents to a total-population (n = 6046) mail survey, 336 (176 case-patients and 160 controls) were randomly selected for clinical evaluation.Measurements: Current cardiac symptoms and major or minor abnormal electrocardiographic features, including heart rate; rhythm; axis; PR, QRS, and QT intervals; QRS structure; atrioventricular blocks; and ST-segment and T-wave changes.Results: Persons with Lyme disease (case-patients, n = 176) (mean duration from disease onset to study evaluation, 5.2 years) and persons without evidence of previous Lyme disease (controls, n = 160) did not differ significantly in their patterns of current cardiac symptoms and electrocardiographic findings, including heart rate (P > 0.2), PR interval (P = 0.15), QRS interval (P > 0.2), QT interval (P > 0.2), axis (P > 0.2), presence of arrhythmias (P > 0.2), first-degree heart block (P = 0.12), bundle-branch block (P > 0.2), and ST-segment abnormalities (P > 0.2). In multivariate analyses that adjusted for age, sex, and previous heart disease, a history of previously treated Lyme disease was not associated with either major (odds ratio, 0.78; P > 0.2) or minor (odds ratio, 1.09; P > 0.2) electrocardiographic abnormalities.Conclusion: Persons with a history of previously treated Lyme disease do not have a higher prevalence of cardiac abnormalities than persons without a history of Lyme disease. [ABSTRACT FROM AUTHOR]

Objective: To assess the ability of echocardiographic data to predict important functional status outcomes in patients with chest pain.Design: Prospective cohort study.Setting: A large, urban teaching hospital.Patients: Three hundred thirty-three patients admitted from the Emergency Department for evaluation of chest pain.Measurements and Main Results: Patients underwent two-dimensional and Doppler echocardiography as well as a face-to-face interview during their initial hospitalization and a telephone interview 1 year thereafter. The interview included the Medical Outcomes Study 36-Item Short Form (SF-36) health inventory, a generic health status instrument with a physical function subscale. The relation between clinical and echocardiographic factors and functional status was explored by univariable and multivariable linear regression and logistic regression analyses. Multiple clinical and echocardiographic factors correlated significantly with functional status measures at 1 year. For the SF-36 score at 1 year, age, male gender, white race, the presence of rales, and a comorbidity score were independently predictors in multivariate analysis; echocardiographic findings of severe left ventricular dysfunction (parameter estimate [PE] -27.6; 95% confidence interval [CI] -43.1, -12.2) and aortic insufficiency (PE -16.7; 95% CI -26.4, -7.0) added independent predictive information. Explanatory power (r2) for models using clinical and demographic variables was .27 and increased after inclusion of echocardiographic data to an r2 of .35. Results in the subset of patients (n = 148) with acute coronary syndromes such as unstable angina or myocardial infarction were qualitatively similar. Selected factors (rales on examination, electrocardiographic changes suggestive of ischemia, and moderate to severe mitral regurgitation) also predicted which patients would die or have a decline in their functional status. In multivariate analysis, only rales remained an independent predictor of poor outcome (odds ratio 2.4; 95% CI 1.2, 4.5).Conclusions: Echocardiographic data are correlated with measures of functional status in patients with chest pain, but the ability to predict future functional status from clinical or echocardiographic information is limited. Because functional status cannot be predicted adequately from either patients' characteristics or echocardiographic testing, it must be assessed directly. [ABSTRACT FROM AUTHOR]

Purpose: Patients with diabetes and acute chest pain may be admitted to hospitals more frequently than patients without diabetes because physicians suspect atypical presentations for ischemic heart disease. This study aimed to determine whether the presentation of acute myocardial infarction and risk for major cardiac complications differs among patients without known coronary artery disease who do or do not have diabetes.Patients and Methods: Data from an emergency department of an urban teaching hospital on the medical histories, physical examinations, and electrocardiograms of 2,694 subjects with acute chest pain and without known coronary artery disease were prospectively recorded.Results: Diabetes was present in 301 (11%) patients. Compared with patients without diabetes, patients with diabetes were more likely to be < or = 60 years old (51% versus 20%) and to have a history of hypertension (70% versus 35%) or high blood cholesterol (35% versus 19%). A discharge diagnosis of acute myocardial infarction was made in 25 diabetic (8%) and in 148 nondiabetic (6%; P = 0.16) patients. A major cardiac complication occurred in two patients with diabetes (0.7%) and in 20 patients without diabetes (0.8%; P = 1.0). Patients with and without diabetes who had atypical chest pain complaints had similar rates of myocardial infarction (3% and 4%, respectively; P = 0.6). Patients with diabetes were more likely to be hospitalized (67% versus 47%; P = 0.001) both before and after adjusting for clinical and electrocardiographic data.Conclusions: For patients with acute chest pain without a prior history of coronary artery disease, diabetes was not associated with a higher rate of acute myocardial infarction or complications. However, diabetes was associated with a higher rate of hospitalization in this population, suggesting that physicians have a lower threshold for admission to the hospital of patients with diabetes. [ABSTRACT FROM AUTHOR]

Doppler echocardiography is often used in evaluating patients with chest pain, but information on prognostic value of this testing and data to help guide selective use are limited. We prospectively studied 448 patients admitted from the emergency department for acute chest pain to assess the utility of qualitative echocardiographic data in predicting long-term survival and the incremental value of this information over routine clinical and electrocardiographic data. Doppler echocardiograms, recorded an average of 21 hours after presentation, were analyzed independently by 2 echocardiographers for global left and right ventricular function and valvular disease. Regional function was assessed by wall motion index. Data on long-term survival were collected with an average follow-up of 35.0 +/- 12.1 months. In univariate Cox regression analysis, left ventricular function and size, wall motion index, right ventricular function, and aortic, mitral, and tricuspid insufficiency were significant predictors of total and cardiovascular mortality. In multivariate analysis, moderate or severe left ventricular dysfunction (mortality rate ratio 3.2, 95% confidence intervals 1.8 to 5.8] and more than mild valvular regurgitation (mortality rate ratio 2.0, 95% confidence interval 1.1 to 3.6) were independent predictors of mortality in a model adjusted for clinical and electrocardiographic data. These factors were more common in patients aged >60 years, in those with prior acute myocardial infarction or angina, and in those with rales on physical examination. In the absence of these clinical characteristics, only 8 of 124 patients (7%) had moderate or severe left ventricular dysfunction or valvular regurgitation. In patients with moderate or severe regurgitation, a murmur was noted on the admission physical examination in 41 of 69 cases (59%). We conclude that echocardiographic evidence of moderate or severe left ventricular dysfunction or valvular regurgitation identifies a high-risk group for overall and cardiovascular mortality in patients with chest pain, and this evidence may not be detected clinically. [ABSTRACT FROM AUTHOR]

The use and interpretation of noninvasive cardiac testing in the elderly may differ from that in younger patients due to changes in disease prevalence, normal values, comorbidities, or patient and physician preferences. This paper reviews the experience with several commonly used noninvasive tests such as electrocardiography, exercise testing, and stress imaging with echocardiography or with scintigraphy in geriatric patients. Most commonly used noninvasive tests remain feasible and safe. Data suggest that exercise stress testing is feasible in many elderly patients with a good safety profile and should be considered as a first-line test due to the extra information provided by the duration and hemodynamic response to exercise. Adjunctive imaging may be particularly helpful when the electrocardiogram is uninterpretable or suspect due to underlying baseline abnormalities or when determining the extent or distribution of ischemia is felt to be important., (Copyright 2003 CVRR, Inc.)

Background: Many noninvasive tests exist to determine whether patients should undergo coronary angiography. The routine use of coronary angiography without previous noninvasive testing is typically not advocated., Objective: To determine the cost-effectiveness of diagnostic strategies for patients with chest pain., Design: Cost-effectiveness analysis., Data Sources: Published data., Target Population: Patients who present with chest pain, have no history of myocardial infarction, and are able to perform an exercise stress test., Time Horizon: Lifetime., Perspective: Societal., Interventions: No testing, exercise electrocardiography, exercise echocardiography, exercise single-photon emission computed tomography (SPECT), and coronary angiography alone., Outcome Measures: Quality-adjusted life expectancy, lifetime cost, and incremental cost-effectiveness., Results of Base-Case Analysis: The incremental cost-effectiveness ratio of routine coronary angiography compared with exercise echocardiography was $36,400 per quality-adjusted life-year (QALY) saved for 55-year-old men with typical angina. For 55-year-old men with atypical angina, exercise echocardiography compared with exercise electrocardiography cost $41,900 per QALY saved. If adequate exercise echocardiography was not available, exercise SPECT cost $54,800 per QALY saved compared with exercise electrocardiography for these patients. For 55-year-old men with nonspecific chest pain, the incremental cost-effectiveness ratio of exercise electrocardiography compared with no testing was $57,700 per QALY saved., Results of Sensitivity Analysis: On the basis of a probabilistic sensitivity analysis, there is a 75% chance that exercise echocardiography costs less than $50,900 per QALY saved for 55-year-old men with atypical angina., Conclusions: Exercise electrocardiography or exercise echocardiography resulted in reasonable cost-effectiveness ratios for patients at mild to moderate risk for coronary artery disease in terms of age, sex, and type of chest pain. Coronary angiography without previous noninvasive testing resulted in reasonable cost-effectiveness ratios for patients with a high pretest probability of coronary artery disease.

Objective: To determine the outcome, safety, and possible cost savings of patients undergoing weekend or holiday exercise treadmill testing., Design: Medical records of all 195 patients scheduled for weekend and holiday exercise testing were reviewed, and 77.9% of patients were contacted by telephone to ascertain medical outcomes and need for further emergency department or inpatient care. Costs were calculated from estimates of days of hospitalization saved and incremental costs incurred in conjunction with weekend or holiday testing., Setting: Urban tertiary care academic medical center., Patients: A total of 195 patients were scheduled for testing, and 181 tests were performed. Over three quarters (75.1%) of patients underwent testing for assessment of chest pain. Other indications included risk stratification after myocardial infarction or coronary angioplasty or prior to noncardiac surgery, or evaluation for arrhythmias, dyspnea, or syncope., Measurements and Main Results: Outcomes included results and complications of testing, hospital course after testing, subsequent emergency department visits and readmissions, myocardial infarction, need for cardiac catheterization or revascularization, and mortality. No complications were noted during testing. In 136 patients tested for the indication of chest pain, 90 (66.2%) had negative tests, 39 (28. 7%) were intermediate, and 6 (4.4%) were positive for ischemia. Same day discharge occurred in 115 (84.6%) of the patients, saving an estimated 185 days of hospitalization ($316.83 per patient tested). Event rates over the 6 months following discharge were low., Conclusions: Weekend and holiday exercise testing is a safe and effective means of risk stratification prior to hospital discharge for patients with chest pain. It also reduces length of stay and is cost saving.

Objective: To assess the ability of echocardiographic data to predict important functional status outcomes in patients with chest pain., Design: Prospective cohort study., Setting: A large, urban teaching hospital., Patients: Three hundred thirty-three patients admitted from the Emergency Department for evaluation of chest pain., Measurements and Main Results: Patients underwent two-dimensional and Doppler echocardiography as well as a face-to-face interview during their initial hospitalization and a telephone interview 1 year thereafter. The interview included the Medical Outcomes Study 36-Item Short Form (SF-36) health inventory, a generic health status instrument with a physical function subscale. The relation between clinical and echocardiographic factors and functional status was explored by univariable and multivariable linear regression and logistic regression analyses. Multiple clinical and echocardiographic factors correlated significantly with functional status measures at 1 year. For the SF-36 score at 1 year, age, male gender, white race, the presence of rales, and a comorbidity score were independently predictors in multivariate analysis; echocardiographic findings of severe left ventricular dysfunction (parameter estimate [PE] -27.6; 95% confidence interval [CI] -43.1, -12.2) and aortic insufficiency (PE -16.7; 95% CI -26.4, -7.0) added independent predictive information. Explanatory power (r2) for models using clinical and demographic variables was .27 and increased after inclusion of echocardiographic data to an r2 of .35. Results in the subset of patients (n = 148) with acute coronary syndromes such as unstable angina or myocardial infarction were qualitatively similar. Selected factors (rales on examination, electrocardiographic changes suggestive of ischemia, and moderate to severe mitral regurgitation) also predicted which patients would die or have a decline in their functional status. In multivariate analysis, only rales remained an independent predictor of poor outcome (odds ratio 2.4; 95% CI 1.2, 4.5)., Conclusions: Echocardiographic data are correlated with measures of functional status in patients with chest pain, but the ability to predict future functional status from clinical or echocardiographic information is limited. Because functional status cannot be predicted adequately from either patients' characteristics or echocardiographic testing, it must be assessed directly.

The optimal role of Doppler echocardiography in the evaluation of patients with acute chest pain syndromes is unclear. We prospectively studied a cohort of 466 patients admitted with acute chest pain syndromes to clarify the relation between echocardiographic data and the risk of serious predischarge complications, and to determine if echocardiographic data can provide incremental prognostic information beyond clinical and electrocardiographic variables. Doppler echocardiograms, performed an average of 21 hours after presentation, were independently analyzed by 2 echocardiographers for information on global left and right ventricular function and valvular disease. Regional function was assessed by a wall motion index (WMI). A composite complications end point was positive if significant recurrent myocardial ischemia, heart failure, or arrhythmia developed after the echocardiogram. In univariate analysis, left (odds ratio [OR] 2.9, 95% confidence interval [CI] 1.6, 5.1) and right (OR 2.7, 95% CI 1.2, 6.2) ventricular function, left ventricular end-diastolic (OR 1.6/cm, 95% CI 1.1, 2.3) and end-systolic (OR 1.4/cm, 95% CI 1.1, 1.9) dimensions, and WMI (OR 3.0, 95% CI 1.8, 4.8) predicted complications that developed after the echocardiogram. In multivariate analysis, WMI remained an incremental predictor of risk with an OR of 2.2/unit (95% CI 1.2, 3.9) scaled from 1 to 4. Even in the subset of 403 patients without acute myocardial infarction, WMI was associated with an OR of 1.9 (95% CI 1.0, 3.7). We conclude that early echocardiography provides incremental prognostic information concerning risk of subsequent complications in patients hospitalized with chest pain.

Aortic regurgitation is associated with retrograde diastolic flow in the aorta. Echocardiographic quantitative analysis of the magnitude of the flow reversal is believed to provide an estimate of severity of regurgitant disease despite variations in flow profiles. The purpose of this study was to evaluate the uniformity of flow patterns in the aorta of patients with aortic regurgitation and to investigate the relationship between these profiles and the echocardiographic estimates of flow reversal. Seventeen patients with chronic aortic regurgitation underwent cine-phase magnetic resonance imaging in an axial section through the ascending and descending aorta. The regurgitant fraction in the ascending aorta 4 cm above the aortic valve and the descending aorta were calculated from the velocity maps. These results were compared with data from nine individual sample volumes in the ascending and descending aorta. The magnetic resonance ascending aortic regurgitant fraction was compared with Doppler echocardiographic descending aortic flow velocity patterns. The descending aortic regurgitant fraction correlated only weakly with the ascending aortic regurgitant fraction (descending aortic regurgitant fraction = 0.62% ascending aortic regurgitant fraction + 0.04%; r = 0.75; p < 0.001). Regurgitant proportions in all sample volumes in the descending aorta, but not in the ascending aorta, were significantly related to the ascending aortic regurgitant fraction. The best descending aortic Doppler echocardiographic parameter for predicting ascending aortic regurgitant fraction was the end-diastolic velocity (end-diastolic velocity = 32.2 cm/sec. ascending aortic regurgitant fraction + 1.4 cm/sec; r = 0.94; p < 0.001). Pulsedwave Doppler sampling of descending aortic flow reflects severity of aortic regurgitant disease, in part the result of more uniform blood-velocity profiles in the descending aorta compared with the ascending aorta. The Doppler end-diastolic velocity in the descending aorta is a useful parameter of severity of aortic regurgitation.

The objective of this study was to identify echocardiographic and clinical predictors of survival after mitral valve surgery when mitral repair is an option. In 132 patients undergoing mitral valve repair or replacement for the diagnosis of mitral regurgitation, preoperative echocardiograms were analyzed quantitatively and reviewed by two independent observers for structural abnormalities of the mitral valve. In Cox regression analysis, clinical factors such as age (mortality rate ratio [MRR] 1.7/decade, 95% confidence intervals [CI] 1.1, 2.4), and New York Heart Association class IV (MRR 3.1, 95% CI 1.4, 6.7) and echocardiographic factors including morphologic evidence of endocarditis or myxomatous disease (MRR 0.3, 95% CI 0.1, 0.7) were significant predictors of overall survival, although valve repair itself was not. End-systolic dimensions and volumes were not, likely related to the small number of patients with markedly increased end-systolic dimensions or volumes (5 patients [4%] with end-systolic dimension > 5.5 cm, 12 patients [9%] with end-systolic volume index > 60 ml/m2). New York Heart Association class IV (MRR 2.9, 95% CI 1.3, 6.4), age (MRR 1.7/decade, 95% CI 1.2, 2.6), and the presence of calcification (MRR 4.6, 95% CI 1.3, 16.2) were independent predictors of survival in multivariate analysis. In this contemporary cohort of patients undergoing repair or replacement for mitral regurgitation, factors such as echocardiographically determined cause of disease and presence of calcification predicted survival; traditional measurements such as end-systolic dimensions and volumes were less predictive, most likely because patients underwent surgery before their ventricles became markedly enlarged. Clinical factors such as age and functional status remained the most potent predictors of survival after surgery for mitral regurgitation.

Objectives: This study sought to identify echocardiographic predictors of survival in patients with chest pain and to assess the utility of qualitative echocardiographic data in the prognostic stratification of this cohort., Background: The potential usefulness of echocardiographic data in prognostic stratification of patients with acute chest pain is unclear, in part because of the qualitative nature of routinely available echocardiographic readings., Methods: The study group comprised 513 patients who underwent transthoracic two-dimensional and Doppler echocardiography within 1 month of emergency department visits for acute chest pain. Clinical and electrocardiographic (ECG) data were recorded for these patients at the time of their initial evaluations, and echocardiographic data were subsequently obtained from the official hospital reports. Follow-up survival rate data were obtained from medical records or the Massachusetts Bureau of Vital Statistics., Results: A mean of 28.5 months after the index visit, 102 patients (20%) had died, including 58 (57%) for whom the primary cause of death was cardiovascular. In analysis of routinely available qualitative echocardiographic data, left ventricular size and function, the presence of regional wall motion abnormalities, mitral regurgitation and structural abnormalities of the mitral valve were significant univariate correlates of both overall mortality and death from cardiovascular causes. Severe left ventricular dysfunction (adjusted rate ratio 3.8, 95% confidence interval [CI] 1.9-7.5) and moderate or severe mitral regurgitation (adjusted rate ratio 2.4, 95% CI 1.5-3.7) were independent predictors of mortality in a multivariate Cox regression analysis that adjusted for clinical and ECG variables. Moderate or severe left ventricular dysfunction and mitral regurgitation were predictors of mortality in the subset of patients without acute myocardial infarction., Conclusions: Qualitative echocardiographic reports of left ventricular dysfunction and mitral regurgitation were independent correlates of prognosis in patients with acute chest pain, including patients without acute myocardial infarction. Further data are needed to assess the generalizability of these findings and the implications for use of this diagnostic technology.