Previous official documents from the AHA and ACCF218 concluded that patients considered to be at low risk of coronary disease by virtue of atypical cardiac symptoms may benefit from CAC testing to help in ruling out the presence of obstructive coronary disease 218 or that coronary calcium assessment may be reasonable for the assessment of symp- tomatic patients, especially in the setting of equivocal tread- mill or functional testing (Class IIb, LOE: B). The present writing committee believed that additional evidence in suffi- ciently large cohorts of patients establishing the uncorrected diagnostic accuracy of CAC to rule in or rule out high-grade coronary artery stenosis in symptomatic patients was needed. 2.2.4.3. CMR Angiography Although not widely applied, CMR angiography has been performed for the detection of the extent and severity of obstructive CAD. As a result of small coronary artery size, tortuosity, and motion, the diagnostic accuracy of CMR angiography is reduced as compared with CCTA.224 A multicenter, controlled clinical trial of patients referred to invasive angiography revealed that magnetic resonance an- giography had an 81% negative predictive value for exclud- ing CAD.225 Several meta-analyses that included a total of 59 studies have reported diagnostic sensitivity and specificity ranging from 87% to 88% and 56% to 70%, respec- tively,158,226 with reports of a lower accuracy than that of CCTA.164 Variability in diagnostic accuracy with CMR Fihn et al Stable Ischemic Heart Disease: Full Text e379 angiography has been attributed to a lack of uniformity in pulse sequences and the application of varying analytic CMR have shown comparable abilities to detect CAD as compared with CCTA.228 No recommendations for the use of CMR angiography are included in this guideline. 3. Risk Assessment 3.1. Clinical Assessment 3.1.1. 