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When it comes to detecting ischemia, computed tomography (CT) angiography performed just as well as invasive quantitative coronary angiography, a prospective study found.

Both diagnostic tools yielded values that (area under the curve [AUC] 0.75 for CT versus 0.77 for quantitative coronary angiography, P=0.6), according to the investigation published online in JACC: Imaging.

FFR is considered the "gold standard for determining lesion-specific ischemia," noted the study authors, led by , of Los Angeles Biomedical Research Center.

There was no difference between CT and conventional angiography for the detection of ischemia within the left anterior descending artery (AUC 0.71 for CT versus 0.73 for angiography, P=0.6), left circumflex artery (AUC 0.78 versus 0.85, P=0.4), and right coronary artery (AUC 0.80 versus 0.83, P=0.6).

"While this study validates the continued use of invasive angiography for anatomic assessment of stenosis, it strongly supports the use of coronary CT angiography for similar diagnosis," concluded Budoff and colleagues.

Due to lower costs and improved safety, they suggested that the noninvasive tool "may be used as an alternative to assess luminal stenosis and to serve as gatekeeper to FFR measurements in patients presenting with chest pain problems."

"The authors report similar, though modest, diagnostic accuracy for both techniques in this context," said Armin , of Johns Hopkins University, in an accompanying editorial.

But "these results are important because they demonstrate yet again that conventional angiography is not superior to CT for the diagnosis of coronary artery disease -- in this case hemodynamically significant coronary artery disease -- when compared with an independent reference standard," he wrote.

Arbab-Zadeh found that "non-invasive coronary angiography has come a long way and is ready for prime time," though the task remains of completing the last and "most difficult" step: proving CT's value "in patient management compared to the current standard of conventional angiography."

Budoff's investigation was a substudy of , and included 252 patients and 407 vessels.

CT and invasive angiography shared similar rates of diagnostic accuracy (69% versus 71%), sensitivity (79% versus 74%), specificity (63% versus 70%), positive predictive value (55% versus 59%), and negative predictive value (83% versus 82%).

Impressive was the fact that the team "only used percent stenosis estimates by CT but did not take advantage of the abundant options for coronary artery disease assessment, e.g., lumen area, area stenosis, lesion length, and plaque burden assessment. Thus, CT sent only its 'B' team and still held its own compared with our current gold standard for the diagnosis of coronary artery disease," Arbab-Zadeh wrote.

He also noted that emerging technologies may soon eliminate the major disadvantage of CT, that it is less accurate when severe coronary calcification is present. And, Arbab-Zadeh indicated, newer scanners are "less vulnerable to suboptimal heart rate control and allow image acquisition with lower radiation and contrast doses compared with conventional angiography."

Budoff and colleagues acknowledged that one important limitation was that the study was not designed to demonstrate noninferiority. There was, in addition, only one FFR cutoff value for ischemia (0.80) analyzed in the study.

"Regardless, a non-invasive method that produces reliable information on both the anatomy and the functional significance of coronary artery stenosis would decrease the need for invasive coronary angiography, improving the safety, cost, and participant burden to acquire anatomic information," they concluded.

A "daunting task" that will take years to accomplish, Arbab-Zadeh wrote, is convincing "practitioners, payers, and patients that CT coronary angiography is equivalent to diagnostic cardiac catheterization." He emphasized that there is a "need to demonstrate that management decisions based on CT assessment yield the same (or better) results for patients across the entire spectrum of management options."

Already, "patients prefer CT over conventional angiography," Arbab-Zadeh noted. "We are almost there."