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Biomedical subjects

R E Patterson

Publications and source records attributed to R E Patterson.

At least 19 recordsLinked to original sources
PubMed1995

Comparison of cost-effectiveness and utility of exercise ECG, single photon emission computed tomography, positron emission tomography, and coronary angiography for diagnosis of coronary artery disease.

BACKGROUND: To compare cost-effectiveness and utility of four clinical algorithms to diagnose obstructive coronary atherosclerotic heart disease (CAD), we compared exercise ECG (ExECG), stress single photon emission computed tomography (SPECT), positron emission tomography (PET), and coronary angiography. METHODS AND RESULTS: Published data and a straightforward mathematical model based on Bayes' theorem were used to compare strategies. Effectiveness was defined as the number of patients with diagnosed CAD, and utility was defined as the clinical outcome, ie, the number of quality-adjusted life years (QALY) extended by therapy after the diagnosis of CAD. Our model used published values for costs, accuracy, and complication rates of tests. Analysis of the model indicates the following results. (1) The direct cost (fee) for each test differs considerably from total cost per delta QALY. (2) As pretest likelihood of CAD (pCAD) in the population increases, there is a linear increase in cost per patient tested but a hyperbolic decrease in cost per effect and cost per utility unit, ie, increased cost-effectiveness and decreased cost per utility unit. (3) At pCAD < 0.70, analysis of the model indicates that stress PET is the most cost-effective test, with the lowest cost per utility, followed by SPECT, ExECG, and angiography, in that order. (4) Above a threshold value of pCAD of 0.70 (for example, middle-aged men with typical angina), proceeding directly to angiography as the first test showed the lowest cost per effect or utility. This quantitative model has the advantage of estimating a threshold value of pCAD (0.70) at which the rank order of cost-effectiveness and cost per utility unit change. The model also allows substitution of different values for any variable as a way to account for the uncertainties of clinical data, ie, changing costs, test accuracy and risk, etc. This procedure, called sensitivity analysis, showed that the rank order of cost-effectiveness did not change despite changes in several variables. CONCLUSIONS: (1) Estimation of total costs of diagnostic tests for CAD requires consideration not only of the direct cost of the test per se (eg, test fees) but also of the indirect and induced costs of management algorithms based on the test (eg, cost/delta QALY). (2) It is essential to consider the clinical history (pCAD) when selecting the clinical algorithm to make a diagnosis with the lowest cost per effect or cost per utility unit. (3) Stress PET shows the lowest cost per effect or cost per utility unit in patients with pCAD < 0.70. (4) Angiography shows the lowest cost per effect or cost per utility unit in patients with pCAD > 0.70.

Adult↗
PubMed1995

Psychosocial correlates of healthful diets: baseline results from the Working Well Study.

BACKGROUND: This report examines psychosocial factors related to selection of healthful diets. Understanding why people select healthful diets can lead to rational design and evaluation of nutrition intervention programs. METHODS: Data are from 16,287 respondents to the baseline survey for the Working Well Trial, a randomized, controlled trial of worksite-based health promotion. The psychosocial constructs we measured were predisposing factors (beliefs, perceived benefits, and motivation; 5 items, Cronbach's alpha = 0.65) and enabling factors (barriers, norms, and social support; 6 items, Cronbach's alpha = 0.57). The healthful diet outcomes were intakes of fat, fiber, and servings of fruits and vegetables (from a food frequency questionnaire) and intention and self-efficacy to decrease fat and increase fruits and vegetables. RESULTS: Based on a 5-point scale (1 = low to 5 = high), the mean predisposing factor scale score was much higher than the enabling factor scale score (3.77 vs 2.50, P < 0.001). Comparing respondents in the highest category of the predisposing scale to those in the lowest, mean percentage of energy from fat was 22.4% lower (-9 percentage points), fiber was 85.2% higher (+4.6 g/1,000 kcal), and fruits and vegetables were 100% higher (+1.6 servings/day) (all trends, P < 0.001). Associations were similar, but much weaker, for the enabling scale. Multiple regression models, which included covariates related to diet and the predisposing and enabling scales, explained a total of between 13 and 26% of the variance in diet and intention to change diet. After control for covariates, the predisposing scale remained a significant and strong predictor of diet and intention to change diet but the enabling scale explained small and nonsignificant amounts of variance. CONCLUSIONS: Predisposing factors are strong predictors of current diet and intention to change diet. Final results from the Working Well Trial will provide more information on whether enabling factors can be enhanced by intervention and whether these changes result in healthier eating patterns.

Adult↗
PubMed1994

Absence of defects in SPECT thallium-201 myocardial images in patients with systemic hypertension and left ventricular hypertrophy.

Hypertension is common in patients undergoing stress and delayed single-photon emission computed tomography (SPECT) thallium-201 myocardial perfusion imaging. Investigators have reported that patients with end-stage renal disease and left ventricular hypertrophy due to hypertension have diminished lateral/septal count ratios on stress and delayed imaging mimicking lateral myocardial infarction in approximately 35% of patients. Subsequently, hypertension has been cited as a frequent cause of thallium-201 artifacts. The purpose of this study was to compare myocardial SPECT thallium-201 distribution in a broader group of patients with left ventricular hypertrophy resulting from hypertension with normal file subjects in order to determine the prevalence of abnormal studies and to compare the lateral/septal count ratio. Average counts in all myocardial regions in the male study group (n = 16) were compared with those in the normal male file patients (n = 49), with particular attention to the lateral and septal walls. In the group of 16 men with hypertension and left ventricular hypertrophy, as a whole, the mean lateral/septal wall count ratio was 4.4% lower (1.09 +/- 0.07) than that in the normal file (1.14 +/- 0.07; p < 0.01). At 3-hour delay, the ratio was virtually the same in the study group (1.06 +/- 0.09) as in the normal file (1.08 +/- 0.06; p = NS). Most important, for clinical purposes no patient had a defect, defined as a lateral/septal count ratio > 2.0 SD below normal limits. All thallium-201 studies were interpreted as normal. In conclusion, myocardial thallium-201 distribution is normal in patients with left ventricular hypertrophy due to hypertension.

Case-Control Studies↗
PubMed1994

Health lifestyle patterns of U.S. adults.

BACKGROUND: Reaching national health objectives depends upon our ability to encourage the performance of multiple good health behaviors. There are cognitive, social, and biological reasons for expecting health behaviors to cluster. However, few studies have found significant associations among health behaviors, with the exception of the documented link between smoking and alcohol consumption. METHODS: We used cluster analysis to identify population subgroups with similar patterns of diet quality, physical activity, alcohol consumption, and cigarette smoking. This is the first study of health behavior interrelationships to include a measure of overall diet quality and a large sample from a nationally representative survey of U.S. adults. RESULTS: We identified seven health behavior typologies: 10% of the sample (health promoting lifestyle) had an overall healthy lifestyle, 25% had a good diet but sedentary activity level, 18% had fair diet but high activity level (fitness lifestyle). Individuals in the passive lifestyle cluster (25%) had no active health promoting activities but did avoid risk taking health behaviors. Six percent of the sample were in a drinking cluster, 15% in a smoking cluster, and 2% had a hedonic lifestyle characterized by heavy drinking and smoking. These lifestyle clusters could be characterized by demographic and socioeconomic factors. CONCLUSIONS: This research indicates that it is possible to identify a discrete number of health lifestyles in a population sample of U.S. adults. Understanding past, present, and changing health lifestyles may provide insights for health behavior research and information for the development and targeting of public health programs that can impact on multifactorial chronic diseases.

Adult↗
PubMed1994

Diet quality index: capturing a multidimensional behavior.

OBJECTIVE: Data for 5,484 adults (aged 21 years and older) who participated in the 1987-88 Nationwide Food Consumption Survey (NFCS) were used to develop an index of overall dietary intake that related to the major, diet-related, chronic diseases in the United States. The low response rate of the 1987-88 NFCS has raised concerns about potential bias, but this large data set is useful for methodologic studies and research that does not attempt to generalize the results to the US population. ANALYSES: Dietary recommendations from the 1989 National Academy of Sciences publication Diet and Health were stratified into three levels of intake for scoring. Individuals who met a dietary goal were given a score of zero. Those who did not meet a goal, but had a fair diet, were given one point, and those who had a poor diet were given two points. These points were summed across eight diet variables to score the index from zero (excellent diet) to 16 (poor diet). RESULTS: Lower index scores were positively associated with high intakes of other important measures of diet quality (eg, fiber, vitamin C). We found that single nutrients (such as dietary fat) were not necessarily associated with other measures of diet quality. CONCLUSION: We concluded that this index ranking of overall dietary patterns was reflective of total diet quality, though substantial misclassification can result from using single nutrients or foods as indicators of diet quality.

Adult↗
PubMed1994

Comparison of modalities to diagnose coronary artery disease.

The purpose of this review is to compare several modalities available for detection of coronary artery disease (CAD). We compare the clinical history, rest/exercise electrocardiogram (ECG), rest/stress left ventricular (LV) function by radionuclide or echocardiographic methods, myocardial perfusion imaging (MPI) by single photon emission computed tomography (SPECT) or positron emission tomography (PET), contrast coronary angiography, magnetic resonance imaging (MRI), spectroscopy (MRS) and angiography (MRA), and ultrafast cine computed tomography (UFCT) to assess LV function, myocardial perfusion, and coronary calcification. We compare the modalities by answering six questions: (1) Does the modality provide unique clinical information? (2) What is the observer error? (3) What are sensitivities and specificities to detect CAD? (4) What patient selection criteria should be applied for each modality? (5) What incremental benefit is obtained from one modality versus another modality? and (6) Where do the modalities fit in the overall scheme of diagnostic testing for CAD? PET MPI appears to be the best noninvasive test for CAD, followed by SPECT thallium-201 and then dobutamine echocardiography. MRA and UFCT may soon play a larger role because they visualize the arteries. Contrast coronary angiography remains the gold standard despite its limitations. Exercise ECG is the least accurate test. The choice of tests critically depends on patient selection--based on clinical history, age, gender, and risk factors to estimate the pretest, clinical probability of CAD.

Coronary Disease↗
PubMed1994

Stages of change in adopting healthy diets: fat, fiber, and correlates of nutrient intake.

The stages of change construct, which addresses the readiness to change, has only recently been applied to dietary behavior, such as fat consumption. This article describes the application of the stages of change construct to dietary fat and fiber consumption and examines the association of dietary stages to eating practices and related demographic and psychosocial factors in a large, geographically diverse population of workers. We present results from the baseline survey of 17,121 employees in the Working Well Trial. We assessed stage from an algorithm based on seven items and measured dietary intake with an 88-item food frequency questionnaire. Findings indicated that a greater proportion of the population has actively tried to reduce fat intake than to consume more fiber. Stage of change was associated with fat, fiber, and fruit and vegetable intake in a stepwise manner, as predicted. In multivariate analyses that controlled for demographic characteristics, stage of change predicted between 8 and 13% of the variance in dietary intake, and more than demographic variables. These findings have implications for the design of nutrition interventions and for the evaluation of intermediate outcomes.

Adult↗
PubMed1994

Defects on SPECT "perfusion" images can occur due to abnormal segmental contraction.

UNLABELLED: Technetium-99m-sestamibi images reflect tracer distribution at the time of injection. This "stay put" indicator allowed us to separate the effects of segmental left ventricular dysfunction per se versus myocardial blood flow on SPECT "perfusion" images in ten dogs. METHODS: An electromagnetic flow probe and hydraulic occluder were placed on the LAD coronary artery. Sonomicrometry was used to measure segmental wall shortening. At peak myocardial blood flow induced by adenosine, 35-45 mCi 99mTc-sestamibi were injected without occlusion. At 1 hr postinjection, during normal contraction, 40-50 msec end-diastolic and end-systolic SPECT images (#1) were acquired to reflect normal myocardial blood flow distribution. Later, during total LAD occlusion, and without reinjection of isotope, another gated scan (#2) was acquired. RESULTS: Coincident with abnormal contraction, large severe systolic defects [(28 +/- 5)% more severe compared to the baseline-scan #1; p < 0.01], and milder diastolic defects [(12 +/- 8)% more severe compared to the baseline-scan #1; p < 0.01] were observed during scan #2. Thus, abnormal contraction alone produced defects on SPECT images. CONCLUSION: Accordingly, defects in myocardial perfusion images must be interpreted as representing the integrated result of the combination of blood flow and segmental contraction heterogeneity.

Adenosine↗
PubMed1993

Intracoronary papaverine but not adenosine reduces regional ventricular function.

OBJECTIVES: Whether intracoronary papaverine or adenosine leads to reductions in regional left ventricular function was tested. METHODS: Fifteen anaesthetised dogs were prepared to record aortic pressure, left ventricular pressure dP/dt, electrocardiogram, regional ventricular shortening, and phasic and mean left circumflex coronary blood flow, and to give intracoronary boluses of papaverine (2, 4, or 6 mg) or adenosine (0.37 and 1.87 mg). RESULTS: Injected doses were chosen to mimic those given in the clinical setting. Papaverine (6 mg) reduced aortic pressure (mean 96(SD 17) to 89(18) mm Hg; p < 0.05), segmental shortening of the infused left circumflex zone (12(5) to 7(9)%; p < 0.05), and area of the pressure-length loop of the infused zone (120(71) to 53(47) mm.mm Hg; p < 0.05). Papaverine increased coronary blood flow (48(25) to 259(95) ml.min-1; p < 0.05), coronary vascular conductance (0.40(0.20) to 2.93(0.94) ml.mm Hg-1.min-1; p < 0.05), heart rate (88(27) to 100(28) beats.min-1; p < 0.05), and the segmental shortening (17(6) to 19(3)% p < 0.05) and area of the pressure-length loop (130(32) to 177(33) mm.mm Hg; p < 0.05) of the non-infused left anterior descending region. The hyperaemia elicited by papaverine was greater than that of reactive hyperaemia (p = 0.008). Papaverine also increased the QT interval corrected for heart rate (0.35(0.04) to 0.45(0.05) s; p < 0.05). When adenosine was given, coronary blood flow and coronary vascular conductance were increased to similar degrees as those during reactive hyperaemia (41(12) to 210(75) ml.min-1 and 0.46(0.14) to 2.43(0.83) mm Hg.ml-1.min-1, respectively; NS). No effects on segmental shortening or the area of the pressure-length loop in either zone were found. Also, adenosine had no effect on the QT interval. CONCLUSIONS: These adverse effects of intracoronary papaverine have important implications in its use in patients, particularly in those in whom abnormal cardiac function already exists. Adenosine, on the other hand, seems to be without deleterious effects.

Adenosine↗
PubMed1992

Comparison of single-photon emission computed tomographic (SPECT) myocardial perfusion imaging with thallium-201 and technetium-99m sestamibi in dogs.

OBJECTIVES: The purpose of the present study was to compare single-photon emission computed tomographic (SPECT) myocardial images of technetium-99m (Tc-99m) sestamibi and thallium-201 (Tl-201) isotopes in the same dog undergoing partial coronary occlusion during pharmacologic vasodilation. BACKGROUND: To date, no controlled study has been reported comparing SPECT Tc-99m sestamibi with SPECT Tl-201 imaging during stress with anatomic and physiologic standards. METHODS: Mongrel dogs were anesthetized with chloralose and instrumented to record left anterior descending coronary blood flow and aortic pressure. Partial coronary occlusion with a hydraulic cuff reduced coronary vascular conductance, which is equal to the coronary blood flow normalized to aortic pressure during peak vasodilation with intravenous adenosine. Each dog received 5 mCi of Tl-201, then 30 mCi of Tc-99m sestamibi during partial coronary occlusion at peak vasodilation. Tomographic myocardial imaging was performed in a 180 degrees anterior arc scan for 33.5 min, first with Tl-201, and later, without moving the dog, for 33.5 min with Tc-99m sestamibi. Postmortem staining defined the region underperfused because of its dependence on the artery that was partially occluded. RESULTS: In seven dogs with moderate reduction in coronary blood flow, coronary vascular conductance decreased with partial coronary occlusion (47 +/- 12%) during Tl-201 imaging and (47 +/- 8%, p = NS) during Tc-99m sestamibi imaging. The underperfused region was 23.9 +/- 6.4% of total left ventricular mass. Counts in the defects were 39% higher (0.86 +/- 0.08 of normal counts) for Tc-99m sestamibi than for Tl-201 (0.64 +/- 0.09 of normal counts, p < 0.001), and the defect on SPECT Tc-99m sestamibi images occupied only a fraction (0.37 +/- 0.30) of the area of the defect on the Tl-201 images of the same dog. Bull's-eye displays constructed from the pathologic slices showed that the Tl-201 defect size was closer to the underperfused region of the left ventricular mass determined pathologically than was the Tc-99m sestamibi defect size. In four additional dogs a severe, near total coronary occlusion was created during Tl-201 and Tc-99m sestamibi administration. In these dogs, similar defect contrast (0.55 +/- 0.12 vs. 0.62 +/- 0.09, p = NS) and areas (0.18 +/- 0.07 vs. 0.18 +/- 0.11, p = NS) were observed with Tl-201 and Tc-99m sestamibi, respectively. CONCLUSIONS: Tomographic myocardial imaging with Tc-99m sestamibi during moderately severe partial coronary occlusion underestimated the area of the defect relative to Tl-201 or to the pathologic reference standard in dogs. Defect contrast was sharper with tomographic myocardial Tl-201 than with tomographic myocardial Tc-99m sestamibi during moderately severe partial coronary occlusion.

Adenosine↗
PubMed1992

Dietary changes in older Americans, 1977-1987.

This study compares dietary practices of persons aged greater than or equal to 65 y surveyed as part of the 1977-78 and 1987-88 Nationwide Food Consumption Surveys. Intakes of high-fat beef and pork, whole milk, and white bread decreased with increases in low-fat beef, pork, poultry and fish, low-fat milk, and whole-grain breads. However, consumption of many important sources of calories and fat (high-fat desserts, butter, and margarine) and fiber (fruits, high-fiber cereals, and vegetables) changed little between 1977 and 1987. The food-consumption trends translated into modest changes in overall nutrient intake. Gender differences were small and contradict the prevailing feeling that women are changing their diets more rapidly than are men. The authors suggest that public health messages have focused too heavily on foods to avoid while not giving adequate guidance for how to plan and prepare meals that will enable older Americans to meet the current diet and health recommendations.

Aged↗
PubMed1992

Neuropeptide Y and coronary vasoconstriction: role of thromboxane A2.

We previously reported that coronary constriction following neuropeptide Y (NPY) was alleviated by cyclooxygenase blockade. To determine the role of thromboxane A2 (TxA2), anesthetized dogs received two paired doses of NPY given 2 h apart. Nine control dogs received NPY alone. Nine test dogs received one of three TxA2 receptor antagonists given between the doses of NPY. Also, five dogs received NPY during which prostaglandins were measured. In controls, NPY decreased coronary blood flow and increased aortic pressure; coronary resistance was increased significantly. Heart rate fell, and myocardial oxygen consumption was unchanged. Thromboxane receptor blockers significantly relieved the coronary constrictor effect of NPY. The reduction in coronary blood flow was blunted, while heart rate, first derivative of left ventricular pressure, and myocardial oxygen consumption were unchanged. Alleviation by TxA2 receptor blockade paralleled that reported for cyclooxygenase inhibitors. Also, significant increases in coronary venous TxA2 were seen at the time of maximal increases in coronary resistance, while prostacyclin was unchanged. In summary, TxA2 appears to mediate part of the coronary constrictor effect of NPY.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1991

Effects of time required for reperfusion (thrombolysis or angioplasty, or both) and location of acute myocardial infarction on left ventricular functional reserve capacity several months later.

The purpose of this study was to determine whether reperfusion of acute myocardial infarction (AMI) by recombinant tissue-type plasminogen activator (rt-PA) or percutaneous transluminal coronary angioplasty, or both, would improve left ventricular (LV) function when it is measured several months later at rest or maximal bicycle exercise, or both. Radionuclide angiography was performed in 44 patients 5 months (range 6 weeks to 9 months) after AMI to assess function, and tomographic myocardial thallium-201 imaging was performed at maximal exercise and delayed rest to determine whether there was any evidence of myocardial ischemia. As expected, no patient had chest pain or redistribution of a thallium defect during the exercise test, because patients had undergone angioplasty (n = 28) or coronary bypass graft surgery (n = 5) where clinically indicated for revascularization. The LV ejection fraction was plotted as a function of the time elapsed between the onset of chest pain and the time when coronary angiography confirmed patency of the infarct-related artery (achieved in 91% of 44 patients by rt-PA [n = 31] or percutaneous transluminal coronary angioplasty [n = 9] ). Functional responses differed markedly between patients with anterior (n = 20) versus inferior (n = 24) wall AMI. LV ejection fraction during exercise correlated with time to reperfusion in patients with an anterior wall AMI (r = -0.58; standard error of the estimate = 11.9%; p less than 0.02) but not in patients with an inferior AMI (r = 0.10; standard error of the estimate = 13.1%; difference not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1991

Haemodynamic effects of intracoronary neuropeptide Y in dogs: resistance to alpha adrenergic blockade.

STUDY OBJECTIVE: Neuropeptide Y is a peptide isolated from brain and neural tissue around human coronary arteries. It has been shown to produce coronary vasoconstriction and myocardial ischaemia. The purposes of this study were (a) to determine whether the vasoconstriction induced by neuropeptide Y was mediated by alpha adrenergic receptors in vivo, and (b) to determine the time course of the effect and whether it was reproducible with a second administration. DESIGN: Neuropeptide Y (200 micrograms over 2 min) was given by intracoronary injection on two occasions 1 h apart to group I dogs (control). In group II the second dose was preceded by treatment with the alpha blocker phenoxybenzamine (4-10 mg.kg-1). The time course and magnitude of the effect was studied in the two groups to determine the effects of alpha blockade and of repeated neuropeptide Y dosage. EXPERIMENTAL MATERIAL: 14 mongrel dogs (n = 7 per group) were anaesthetised with chloralose for a left thoracotomy to measure coronary blood flow, aortic pressure, left ventricular pressure, and heart rate. MEASUREMENTS AND MAIN RESULTS: Reproducible prolonged increases in coronary vascular resistance occurred after the first [33(SD 18)%] and second [34(17)%] doses of neuropeptide Y. At this infusion rate mean aortic pressure increased with each dose by 21% and coronary blood flow decreased by 7%. In group II dogs, phenoxybenzamine given intravenously 20 min after the first dose of neuropeptide Y reduced mean aortic pressure by 15-20 mm Hg. In this group neuropeptide Y also caused reproducible increases in coronary vascular resistance before (36%) and after (46%) alpha blockade. CONCLUSIONS: Neuropeptide Y constricts coronary arteries in vivo by mechanisms that do not require intact alpha adrenergic receptors, and the coronary vasoconstriction was prolonged and reproducible.

Animals↗
PubMed1991

Adenosine receptor blockade with 8-p-sulfophenyltheophylline aggravates coronary constriction.

We examined the role of adenosine in modulating the coronary constrictor effect of neuropeptide Y (NPY). Anesthetized dogs (n = 22) were instrumented to record hemodynamics and to collect arterial and coronary venous blood. In control dogs (n = 7), during the first 30 min before NPY, baseline coronary resistance fell slightly. By 10 min after NPY (42 nmol over 4 min), coronary resistance was increased by 30% and fell slowly to pre-NPY levels over the ensuing hour. Intravenous (7.5 mg/kg, n = 3) or intracoronary (to 100 microM arterial concentration, n = 12) infusion of 8-p-sulfophenyltheophylline (8-THEO) blocked the vasodilator effects of adenosine but did not alter the peak dilation seen with papaverine or reactive hyperemia. Over 30 min before NPY, infusion of 8-THEO increased baseline resistance by 31% as it reduced coronary blood flow, despite no change in other hemodynamic parameters or myocardial oxygen consumption. The coronary constrictor effect of NPY was magnified in the presence of adenosine receptor blockade. At 3 min, coronary resistance was increased by 34%, at 5 min by 52%, and at 10 min by 59%. The effect of adenosine receptor blockade on constriction due to NPY could not be attributed to a nonspecific alteration in cardiac function or oxygen consumption. In addition, the increase in baseline coronary resistance following receptor blockade correlated with the worsening of the coronary constriction following NPY (r = 0.48, P less than 0.05). Thus it appears that adenosine modulates an imposed constriction of coronary vessels and acts as a "host defense" to restore coronary tone toward normal.

Adenosine↗
PubMed1989

Importance of epidemiology and biostatistics in deciding clinical strategies for using diagnostic tests: a simplified approach using examples from coronary artery disease.

The explosion of costly new medical diagnostic technologies demands a common sense approach to help physicians decide appropriate indications and strategies for use of these tests. This simple, nonmathematical review focuses on the assessment of coronary artery disease, but the approach can be generalized to other medical problems. This clinical approach to diagnostic testing strategies is based on seven sequential questions: 1. What is the clinical probability that this patient has a specific disease characteristic based on clinical data? 2. What is the overall objective for management of this patient based on the overall status of the patient? 3. Most importantly, what specific questions need to be answered about the patient's condition before the physician can recommend the most appropriate management (e.g., whether the patient has coronary disease, whether an anatomic lesion is functionally significant, whether a myocardial region is reversibly ischemic or irreversibly infarcted, whether a particular therapy has had good or bad effects or what is the patient's prognosis)? The key point is for the physician to formulate a specific clinical question about the patient before the test. 4. The physician must then ask how well does the test answer the particular clinical question about the patient. Here the physician needs to understand the sensitivity and specificity of the test, especially because they are influenced by various clinical biases. 5. Next, the physician must ask how to interpret the reliability of a positive or negative test result in the individual patient. This requires understanding predictive value and predictive error of a given result and how they are influenced by the clinical data as described by Bayes' theorem. 6. Next, the physician must ask what further tests or therapies will be recommended for the patient. The physician can estimate in advance how different test results would alter management plans and he can then allow this estimate to help determine indications for the test. There is some controversy concerning whether to use Bayes' theorem or multivariate analysis to estimate the final probability of a disease characteristic. 7. Finally, in this era of quality assurance, professional review and cost containment, it behooves each physician to ask whether the data provided by the particular tests were worth the cost, inconvenience and risk for that particular patient.

Bayes Theorem↗