Duke treadmill score: the formula and risk groups (Mark 1991)
The Duke treadmill score combines three results from a Bruce-protocol exercise test into one number: how long the person exercised, how far the ST segment moved and whether angina appeared. Longer exercise raises the score; ST deviation and angina lower it. This Duke treadmill score calculator applies the Mark 1991 formula and reports the group the result falls in.
Not a medical device. Not a diagnosis or dosing recommendation.
What is the Duke treadmill score?
It's a weighted sum reported by Mark and colleagues in outpatients with suspected coronary artery disease. Each millimetre of ST deviation costs 5 points and each step on the angina index costs 4, set against one point per minute of exercise.
The calculator takes the three results as numbers you supply. It doesn't read the ECG or run the test.
The Duke treadmill score formula
Duke treadmill score = exercise minutes
− 5 × ST deviation (mm)
− 4 × angina index
angina index: 0 none, 1 nonlimiting, 2 exercise-limiting
rounded to 1 decimalExact expression the calculator uses:
duke_treadmill_score = exercise_min - (5 * st_deviation_mm) - (4 * angina_index)Inputs
| Input | Meaning | Range |
|---|---|---|
exercise_min | Exercise time on the Bruce protocol, minutes | 0 to 21 |
st_deviation_mm | Largest net ST-segment deviation during or after exercise, mm | 0 to 10 |
angina_index | 0 no angina, 1 nonlimiting angina, 2 angina that stopped the test | 0, 1 or 2 |
How the calculation works
- Start with exercise time in minutes.
- Subtract 5 for every millimetre of ST deviation.
- Subtract 4 for each step on the angina index.
- Round to one decimal.
- Assign the group on the rounded score:
| Score | Group |
|---|---|
| Below -10 | high |
| -10 to 4 | moderate |
| 5 or more | low |
The groups are the ones Mark 1991 used to describe its cohort. The score can be negative.
Worked examples
These use Magent's own expected values for the calculator.
Example 1: 10 minutes, 1 mm, no angina
- 10 − 5 × 1 − 4 × 0 = 5.
- Duke treadmill score 5.0, group
low.
Example 2: 5 minutes, 2 mm, nonlimiting angina
- 5 − 5 × 2 − 4 × 1 = -9.0.
- -9.0 is between -10 and 4.
- Duke treadmill score -9.0, group
moderate.
Example 3: 3 minutes, 2 mm, exercise-limiting angina
- 3 − 5 × 2 − 4 × 2 = -15.0.
- -15.0 is below -10.
- Duke treadmill score -15.0, group
high.
History of the Duke treadmill score
Mark and colleagues published "Prognostic value of a treadmill exercise score in outpatients with suspected coronary artery disease" in the New England Journal of Medicine in 1991. The paper set out the weights and the three groups that the calculator uses.
When it's used
After a Bruce-protocol exercise test, when the three results are summarised as a single number for reporting or discussion.
Where it's used
Exercise testing laboratories, cardiology clinics and chest pain services.
Who uses it
Cardiologists, exercise physiologists and the staff who report stress tests. The calculator does the arithmetic.
Limits of the calculation
- It's built around the Bruce protocol. Times from other protocols don't carry over.
- ST deviation and the angina index are judgements made during the test; the calculator takes them as given.
- The groups describe the 1991 cohort. They don't identify coronary artery disease, and the calculator doesn't advise on further testing.
- This page doesn't say what a score means for a particular person.
Clinical decisions belong to a qualified clinician who knows the patient.
How it differs from related calculators
- HEART score uses history, ECG, age, risk factors and troponin, not exercise test results.
- TIMI risk score for STEMI grades risk after an ST-elevation infarction.
- Modified Sgarbossa criteria apply to ECGs with left bundle branch block.
Glossary
- Bruce protocol: a treadmill test whose speed and incline rise in stages.
- ST deviation: a shift of the ST segment of the ECG above or below baseline.
- Angina index: 0 for none, 1 for angina that didn't stop the test, 2 for angina that did.
Common mistakes
- Adding the ST term instead of subtracting it. Each millimetre lowers the score by 5.
- Using a different protocol's minutes. The weights assume the Bruce protocol.
- Reading a low score as good. Lower scores fall in the higher-risk group.
Source
Mark DB, et al. Prognostic value of a treadmill exercise score in outpatients with suspected coronary artery disease. N Engl J Med. 1991;325(12):849-853. DOI: 10.1056/NEJM199109193251204. PMID: 1875969
Frequently asked questions
How is the Duke treadmill score calculated?
Exercise minutes minus 5 times the ST deviation in millimetres minus 4 times the angina index.
What are the Duke treadmill score groups?
Below -10 is high, -10 to 4 is moderate and 5 or more is low.
Can the score be negative?
Yes. ST deviation and angina can outweigh the exercise time.
Does the calculator read the exercise ECG?
No. You enter the ST deviation and the angina index.