Formula and Method for the Duke Treadmill Score
The Duke Treadmill Score (DTS) is a well-validated clinical index that combines three results from a standard exercise treadmill test into a single number used to estimate cardiovascular risk in people with suspected coronary artery disease. It was developed by Mark and colleagues (Duke University, published in the New England Journal of Medicine, 1991) from thousands of patients undergoing Bruce-protocol treadmill testing and remains one of the most widely cited exercise-test risk scores in cardiology. The formula is: DTS = Exercise time (minutes) − (5 × maximal ST-segment deviation, mm) − (4 × treadmill angina index). This calculator is an educational tool for exploring that formula and is not a diagnostic device — the actual score used for patient care should be calculated and interpreted by the clinician who supervised and read the stress test.
How the calculation works
Enter the total exercise time in minutes achieved on the standard Bruce protocol, the maximal ST-segment deviation observed on the ECG during or after exercise (measured in millimeters, in the lead with the greatest deviation, excluding aVR), and the angina index describing chest pain during the test: 0 if no angina occurred, 1 if angina occurred but did not require stopping the test, or 2 if angina was severe enough to be the reason the test was stopped. The calculator multiplies the ST deviation by 5, the angina index by 4, subtracts both from the exercise time, and reports the resulting score along with its risk category.
Interpreting the risk categories
- Low risk (score ≥ +5): approximately 99% 5-year survival and about 0.25% average annual cardiac mortality in the original validation cohort.
- Moderate risk (score −10 to +4): approximately 95% 5-year survival and about 1.25% average annual cardiac mortality.
- High risk (score ≤ −11): approximately 79% 5-year survival and about 5% average annual cardiac mortality — these patients are more likely to be referred for further cardiac evaluation, such as coronary angiography.
Important considerations
The Duke Treadmill Score was derived and validated using the standard Bruce protocol; if a different protocol or treadmill speed/grade schedule was used, exercise time should first be converted to a Bruce-equivalent time (for example via estimated METs) before applying this formula. The score also assumes an interpretable ECG (it is less reliable with baseline left bundle branch block, paced rhythms, or resting ST abnormalities) and was validated primarily in patients referred for evaluation of suspected, not confirmed, coronary artery disease. This tool is for educational and informational purposes only, is not a substitute for professional medical advice, and should not be used on its own to diagnose or guide treatment — always discuss stress test results with the ordering physician or a cardiologist.