The Duke Treadmill Score (DTS) is a number calculated from the results of a standard treadmill stress test. It combines three pieces of information, exercise duration, heart rhythm changes, and chest pain during the test, into a single score that estimates your risk of coronary artery disease. Doctors use it to decide whether you need further testing, like imaging or catheterization, or whether your results are reassuring enough to monitor without intervention.
How the Score Is Calculated
The Duke Treadmill Score uses a straightforward formula:
DTS = exercise time − (5 × ST deviation) − (4 × angina index)
Each component captures something different about how your heart responded to exertion:
- Exercise time is measured in minutes using the standard Bruce protocol, the most common treadmill test format where speed and incline increase every three minutes. Longer exercise time is better, because it means your heart can handle more work.
- ST deviation is the largest change, measured in millimeters, in a specific part of your heart’s electrical signal during or after the test. This change suggests parts of your heart muscle may not be getting enough blood flow. A larger deviation pulls your score down.
- Angina index reflects whether you experienced chest pain during the test. It’s scored as 0 if you had no chest pain, 1 if you had chest pain that didn’t force you to stop, and 2 if chest pain was the reason the test ended. Any chest pain lowers the score, and pain severe enough to stop the test lowers it substantially.
As an example, someone who exercises for 9 minutes, has 1 mm of ST deviation, and experiences no chest pain would score 9 − (5 × 1) − (4 × 0) = 4. Someone who only lasts 4 minutes, has 2 mm of ST deviation, and stops because of chest pain would score 4 − (5 × 2) − (4 × 2) = −14.
What the Score Means
Duke scores are grouped into three risk categories:
- Low risk: A score of +5 or higher. This group has an estimated annual mortality rate under 1% and roughly a 99% five-year survival rate. Most people in this category do not need further invasive testing.
- Moderate risk: A score between −10 and +4. This group has an intermediate probability of significant coronary artery disease, and doctors typically consider additional imaging or testing based on the full clinical picture.
- High risk: A score of −11 or lower. This group has the highest likelihood of severe coronary artery disease and is often referred for coronary angiography, the catheter-based procedure that directly visualizes the heart’s arteries.
Research on the score’s accuracy found that a cutoff of roughly −3.7 correctly identified significant coronary artery disease about 74% of the time, while correctly ruling it out about 73% of the time. For detecting the most severe disease, a cutoff around −11 was accurate about 80% of the time in both directions.
How It Performs in Women vs. Men
One common concern with cardiac testing is whether results are equally reliable in women and men. Research published in the Journal of the American College of Cardiology found the Duke score works well in both, and in some ways performs better in women. Among women classified as low risk by the score, only 20% turned out to have significant coronary artery disease on further testing, compared with 47% of low-risk men. Severe disease (blockages in three vessels or the left main artery) was found in just 3.5% of low-risk women versus 11.4% of low-risk men.
Women in these studies tended to score higher overall (average 1.6 versus −0.3 for men), reflecting lower rates of coronary disease in the populations studied. The score stratified both genders effectively into prognostic categories, meaning it reliably separated people at higher and lower risk regardless of sex.
When the Score Is Most Useful
The Duke score works best in people who can exercise adequately on a treadmill and who have a normal or near-normal resting electrocardiogram. Certain baseline abnormalities in the heart’s electrical pattern can make the ST-deviation component unreliable. Conditions like left bundle branch block, a pacemaker rhythm, or the effects of certain heart medications can alter the resting electrical signal in ways that mimic or mask the changes the score relies on. In those situations, doctors typically skip the standard treadmill test entirely and opt for stress imaging instead.
The score is also designed for people being evaluated for coronary artery disease, not for those who already have a confirmed diagnosis or have previously had stents or bypass surgery. In those populations, different tools are used to assess how the heart is doing.
Duke Score vs. Stress Imaging
A standard treadmill test with a Duke score is simpler, faster, and less expensive than imaging-based stress tests like stress echocardiography or nuclear stress testing. For many patients, it provides enough information to guide the next step. Research comparing the Duke score with stress echocardiography found that the two approaches have complementary value. The Duke score effectively separates patients into risk groups on its own, and stress imaging adds further detail, particularly for patients who fall into the intermediate-risk category.
For patients with a high Duke score (meaning low risk), stress imaging did not add much additional prognostic information. For patients with intermediate scores, stress echocardiography provided significant additional insight, helping to further sort who was truly at higher risk versus who could be managed conservatively. This is why many doctors use the Duke score as a first-pass filter: if the result is clearly low risk, further imaging may be unnecessary, saving time and cost. If the result is intermediate or high risk, imaging or catheterization typically follows.
What Your Score Means for You
If you’ve had a treadmill stress test and your doctor mentions your Duke Treadmill Score, the number itself tells you where you fall on a spectrum. A positive score, especially above +5, is generally reassuring. A negative score, particularly below −10, signals that your heart’s response to exercise raised enough concern to warrant closer investigation. The score doesn’t diagnose coronary artery disease on its own, but it quantifies how much suspicion your test results generate, which helps determine whether the next step is watchful monitoring or a more detailed look at your coronary arteries.