For patients with a low to intermediate pretest probability of obstructive IHD, noncontrast cardiac CT to determine the CAC score may be consid- ered.174 (Level of Evidence: C) See Online Data Supplement 1 for additional data on diag- nostic accuracy of stress testing and advanced imaging for the diagnosis of suspected SIHD. 2.2.3. Diagnostic Accuracy of Nonimaging and Imaging Stress Testing for the Initial Diagnosis of Suspected SIHD 2.2.3.1. Exercise ECG The exercise ECG has been the cornerstone of diagnostic testing of SIHD patients for several decades. The diagnostic endpoint for an ischemic ECG is $1 mm horizontal or down-sloping (at 80 ms after the J point) ST-segment depression at peak exercise. ST-segment elevation (in a non Q-wave lead and excluding aortic valve replacement) during or after exercise occurs infrequently but represents a high-risk ECG finding consistent with an ACS. The diagnos- tic accuracy of exertional ST-segment depression has been studied extensively in several meta-analyses, systematic re- views, large observational registries, and RCTs.114,145 147,175 The composite diagnostic sensitivity and specificity, unad- justed for referral bias, is 61% and ranges from 70% to 77%, but it is lower in women146,147,175 and lower than that for stress imaging modalities. A similar accuracy has been reported for correlation of ECG ischemia with anatomic CAD by CCTA.176 Diagnostic accuracy is improved when consid- eration is given to additional non-ECG factors, such as exercise duration, chronotropic incompetence, angina, ven- tricular arrhythmias, heart rate recovery, and hemodynamic response to exercise (ie, drop in systolic BP), or when combination scores such as the Duke treadmill or Lauer scores are applied.118,177 180 Multiple factors in addition to the patient s inability to achieve maximal exercise levels influence the accuracy of the ECG during exercise testing to diagnose obstructive CAD. 