The ACE Equation Gives Equivalent Mortality Risk Estimates to the Duke Treadmill Score and Duke Nomogram

We sought to develop an equation, the Alma College Estimation (ACE) equation, to estimate survival equivalent to the Duke treadmill score (DTS) and Duke nomogram.

Combinations of ST segment deviation (0, 1, 2, 3, and 4 mm), angina (0 = none, 1 = nonlimiting, and 2 = limiting), and metabolic equivalents of task (2-20) were graphed on the Duke nomogram, and the ACE equation was developed to predict annual mortality likelihood from nomogram measurements. Secondary analyses analyzed data from a clinical cohort of 10,673 patients who underwent a graded maximal exercise test at a county hospital in Sweden between 2005 and 2016. Following ACE equation development, survival estimates were compared between the equation to traditional line plotting on the Duke nomogram using mean absolute error and equivalence testing. Also, 5-year survival estimates from the ACE equation, nomogram, and DTS were categorized into low, intermediate, and high risk and compared using percent agreement.

The developed ACE equation is a non-linear, exponential function. The 5-year survival estimates (100 - [5 × annual mortality risk]) from the ACE equation were significantly equivalent to within 1% of the nomogram ( P < .001, mean difference 0.1% ± 1.0%), with low mean absolute error (all combinations: 0.7% ± 0.7%, clinical cohort: 0.7% ± 1.0%). Percent agreement in risk categories ranged from 83% to 94%.

The ACE equation produced similar survival estimates to the Duke nomogram and DTS. This equation improves precision over the DTS and ease of use over the Duke nomogram, and therefore, may serve as a valuable tool for clinicians assessing prognosis from exercise test findings.