What is the sensitivity, specificity and positive predictive value of an abnormal exercise test?

What is the sensitivity, specificity and positive predictive value of an abnormal exercise test?

While sensitivity (% of those with disease who have an abnormal test) and specificity (% of those without disease who have a normal test) are relatively independent of disease prevalence they are reciprocally related and dependent upon the cut point or criterion chosen for diagnosis. The positive predictive value of an abnormal test (% of those with an abnormal test that have disease) is directly related to the prevalence of disease. Another way to compare the diagnostic characteristics of a test is by use of predictive accuracy that is the percentage of total true calls (both negative and positive). While it is affected by disease prevalence, since diagnostic testing is usually only indicated when the pretest probability is 50% (i.e. a disease prevalence of 50%) this measurement is a simple way of comparing test performance.
Meta-analysis of the exercise test studies with angiographic correlates has demonstrated the standard ST response (1mm depression) to have an average sensitivity of 68% and a specificity of 72% and a predictive accuracy of 69%. But most of these studies have been affected by work up bias that means that those with abnormal tests were more likely to be entered into the studies to be catheterised. When work up bias is removed by having all patients with chest pain undergo catheterisation different results are obtained though the predictive accuracy remains the same. In such a study we found a sensitivity of 45% and a specificity of 85%. It appears that this is how the test performs in the clinic or doctor’s office. However, the inclusion of clinical and other test results in scores can increase the predictive accuracy of the standard exercise test to nearly 90%.

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