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Coronary CT angiography (CCTA) appears to be most valuable in patients with intermediate pretest probability of coronary artery disease (CAD), because the test can distinguish which of these patients need invasive angiography, according to an article published May 18 online in the Annals of Internal Medicine.

Annick C. Weustink, MD, of the Erasmus University Medical Center in Rotterdam, Netherlands, and colleagues explained that in recent years, CCTA has become a popular noninvasive test for diagnosing CAD. The article, based on an observational study, sought to compare the accuracy and clinical utility of stress testing and CCTA for identifying patients who require invasive coronary angiography.

The researchers recruited 517 patients for their study who were referred by their physicians for the evaluation of their chest symptoms through the utilization of stress testing or invasive coronary angiography at the University Medical Center.

In each patient, the diagnostic accuracy of stress testing and CCTA was compared with invasive coronary angiography. The Duke clinical score was employed for the evaluation of pretest probabilities of CAD and clinical utility of noninvasive testing, defined as a pretest or posttest probability that suggests how to proceed with testing, was measured.

According to the authors, no further testing is required if pretest probability of disease was determined to be less than 5 percent. They suggested proceeding with invasive coronary angiography if pretest probability was between 5 and 90 percent and refer directly for invasive coronary angiography if the percentage is above 90 percent.

For CCTA, sensitivity was determined to be nearly 100 percent, but stress testing was not as accurate. For patients presenting with a low pretest probability of CAD, or less than 20 percent, a negative stress test or CCTA result suggested no need for invasive coronary angiography.

Intermediate pretest probability, or for patients presenting with 20 to 80 percent likelihood of CAD, a positive CCTA result suggested need to proceed with invasive coronary angiography. However, for this patient cohort, a negative result suggested no need for further testing.  If a patient presented with a pretest probability of greater than 80 percent, physicians could resort to invasive coronary angiography directly, the authors wrote.

In noting limitations to their research, Weustink and colleagues said that referral and verification bias on part of the physicians referring patients to the study may have influenced the findings.  In addition, “stress testing provides functional information that may add value to that from anatomical (CCTA or ICA) imaging.”

While Weustink concluded that CCTA is most valuable to the intermediate pretest probability patient cohort in determining the individuals that will require more invasive testing, “these findings need to be confirmed before CCTA can be routinely recommended for these patients,” the authors wrote.