Sixty-four slice coronary computed tomography angiography (CCTA) has a negative predictive value of more than 99 percent in excluding major adverse cardiac events (MACE) for 30 days in patients who present with acute coronary syndrome (ACS) symptoms, according to a study published in the December issue of Academic Radiology.
The results demonstrated that CCTA could be highly useful for discharging low to moderate risk patients safely for up to 30 days, according to Kevin M. Takakuwa, MD, of Thomas Jefferson University Hospital in Philadelphia, and colleagues.
Emergency departments saw more than 6.3 million patients complaining of chest pain or related symptoms and nearly 2 million of them were admitted. More than 65 percent of the admitted patients were found to not have ACS, resulting in an estimated loss of $6 to $8 billion per year. While it’s appropriate to admit high-risk patients and discharge very low-risk patients, those in the middle are more difficult to determine a best course of action, according to the researchers.
“A highly accurate diagnostic test that can exclude ACS could potentially save the U.S. healthcare system billions of dollars,” wrote the authors.
The researchers reviewed data acquired from January 2005 and May 2011 in electronic databases and also in reference lists from relevant published research articles. Included in the study were adult patients who presented with symptoms of ACS, had CCTA performed and were then assessed for MACE at 30 days past presentation. A 50 percent diameter stenosis was used as the cutoff criterion for coronary artery disease.
A total of 1,559 patients were studied. All were at low- to intermediate-risk for ACS and all had initial inconclusive electrocardiograms and negative cardiac biomarker tests.
Overall, 14.8 percent of patients had a positive CCTA test. Pooled sensitivity was 93.3 percent, specificity was 89.9 percent and the positive predictive value was 48.1 percent. The negative predictive value was 99.3 percent.
“CCTA appears to be most useful for ruling out ACS in an acute ED setting where patients present with active undifferentiated symptoms suggestive of ACS,” wrote the authors.
“It furthermore has equal or better sensitivity and specificity compared to reported values for exercise stress testing, exercise echocardiography and nuclear stress testing.”
Only 11 of the false-negative patients would have inappropriately discharged to home with ACS. The authors wrote that while there is no true consensus on an acceptable rate for missing ACS, some have proposed it should be set a less than 1 percent.
“Although CCTA is not perfect, we would point out that a test that yields a [negative predictive value] of 99.3 percent for MACE within 30 days in a study population in which 85.2 percent of low to moderate risk for ACS patients ended up with a negative result is better than virtually any other alternative protocol available,” wrote the authors.