Objective: Our aim was to derive and validate a
simplified treadmill score for predicting the probability of
angiographically confirmed coronary artery disease (CAD).
Background: The American College of Cardiology/American
Heart Association guidelines for exercise testing recommend the
use of multivariable equations to enhance the diagnostic
characteristics of the standard treadmill test. Most of these equations
use complicated statistical techniques to provide diagnostic estimates
of CAD. Simplified scores derived from such equations that require
physicians only to add points have been developed for pretest estimates
of disease and for prognosis. However, no simplified score has been
developed specifically for the diagnosis of CAD using exercise test
results.
Methods: Consecutive patients referred for
evaluation of chest pain who underwent standard treadmill testing
followed by coronary angiography were studied. A logistic regression
model was used to predict clinically significant (≥ 50% stenosis)
CAD and then the variables and coefficients were used to derive a
simplified score. The simplified score was calculated as follows:
(6 × maximal heart rate code) + (5 × ST-segment depression code)+
(4 × age code) + angina pectoris code + hypercholesterolemia code+
diabetes code + treadmill angina index code. The simplified score had
a range from 6 to 95, with < 40 designated as low probability,
between 40 and 60 was intermediate probability, and > 60 was high
probability for CAD.
Results: A total of 1,282 male
patients without a prior myocardial infarction underwent exercise
treadmill testing and coronary angiography in the derivation group, and
there were 476 male patients in the validation group from another
institution. The area under the receiver operating characteristic curve
(± SE) for the ST-segment response alone was 0.67 as compared to
0.79 ± 0.01 for the diagnostic score (p > 0.001). The prevalence
of significant disease for the men was 27% in the low-probability
group, 62% in the intermediate-probability group, and 92% in the
high-probability group, which was similar to the prevalence in the
validation group, with 22%, 58%, and 92% in low-, intermediate-, and
high-probability groups, respectively. The low-probability group had< 4% prevalence of severe disease. In both populations, 7 more
patients out of 100 were correctly classified than with the use of
ST-segment criteria. When used as a clinical management strategy, the
score has a sensitivity of 88% and a specificity of 96%.
Conclusion: This simplified exercise score that estimates
the probability of CAD can be easily applied without a calculator and
is a useful and valid tool that can help physicians manage patients
presenting with chest pain.