. World Health Organization :?The primary purpose of an exercise test is to determine the responses of the individual to [exercise] efforts at given levels and from this information to estimate probable performance in specific life and occupational situations.\". . Bayes Theorem states : ?The post
ACSM s Guidelines For Exercise Testing Prescription
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ACSM’s Guidelines For Exercise Testing & Prescription
Interpretation Of Clinical Test Data
World Health Organization :
“The primary purpose of an exercise test is to determine the responses of the individual to [exercise] efforts at given levels and from this information to estimate probable performance in specific life and occupational situations.”
Bayes Theorem states :
“The post-test probability of a patient having disease is determined by the disease probability before the test and by the probability that the test will provide a true result.”
Bayes Theorem speaks to the issue that an exercise test must have two qualities : sensitivity and specificity.
Sensitivity refers to the percent of patients tested who have CAD and who demonstrate a positive (abnormal) test outcome - i.e. - how often the test will identify a sick individual (~ 70%).
Specificity refers to the percent of healthy people without CAD who also demonstrate a negative (normal) stress test - i.e. - how often the test is able to identify a healthy individual (~80%).
False Negative Tests
Failure to reach ischemic threshold
Monitoring an insufficient # of leads
Failure to recognize non-EKG signs & symptoms associated w/ CAD
Collateralization that masks angiographically significant CAD
Technical & observer error
False Positive Tests
Drugs - digitalis preparations
Left Bundle Branch Block
Mitral valve prolapse
Coronary spasm - Prinzmetal angina
The predictive value of exercise testing is a measure of how accurately a test result correctly identifies the presence or absence of CAD in the test population.
Using exercise tests to screen large numbers of asymptomatic people is of questionable value.
Testing individuals with symptoms is a much more practical reason for an exercise test.
Symptoms which make Bayesian senseand which increase the predictive value of an exercise test would be :
Angina, chest discomfort/pressure
Recurrent palpitations w/ exercise
SOB w/ exertion that is unexpected
Dizziness, syncope, vertigo, diplopia w/ ex.
Imaging Stress Tests
Generally speaking, echocardiogaphic studies will slightly improve the sensitivity & specificity of simple GXT’s .
Exercise GXT’s with technetium-Tc99m sestamibi imaging or thallium chloride-201 imaging tend to improve the sensitivity and specificity of the test to ~ 85+%.
The sensitivity and specificity of any test is improved by the number of diseased vessels.