Almost one-fourth of all patients who underwent coronary CT angiography (CCTA) in a multi-center study had extracardiac findings; however, several serious diagnoses were missed with the limited viewing approach, but use of the broad viewing approach led to more workup and follow-up imaging, according to findings in the July issue in the American Journal of Roentgenology.
While a few cardiologists have suggested that the “field of interpretation be restricted to avoid false-positive diagnoses, radiologists generally favor a comprehensive review to avoid false-negative findings,” according to the authors.
As a result, Kevin M. Johnson, MD, from the department of diagnostic radiology at Yale University School of Medicine in New Haven, Conn., and colleagues undertook the study to examine this “tradeoff” by comparing broad and focused approaches of viewing CCTA.
Outpatient CCTA was performed on consecutively registered patients. In the broad approach, the researchers evaluated both the large field-of-view and small field-of-view image sets, including lung windows. In the focused approach, they centered attention on the heart, great vessels and immediately adjacent structures—not including lung windows. They also classified each finding as necessitating immediate therapy, timely additional workup, longer-term follow-up or no action.
Among 6,920 patients, 23.7 percent had one or more extracardiac findings for a total of 1,901 findings in the broad viewing scheme, the researchers reported. Of the 6,920 patients, 16.2 percent had a finding necessitating therapy, workup or follow-up. In the focused viewing scheme, many of these were missed, including 90.9 percent of the findings necessitating therapy, 64.1 percent necessitating workup and 51.2 percent necessitating follow-up.
The use of the focused approach resulted in fewer false-positive diagnoses, according to the authors, but five malignant tumors of the breast, 88 lung infiltrates, 43 cases of adenopathy, two cases of polycystic kidney disease, one breast abscess and one case of splenic flexure diverticulitis were missed.
Use of the broad viewing approach led to further workup of 10.2 percent of the findings and later follow-up of 50.6 percent, Johnson and colleagues reported.
“[M]ost of these findings can be expected to be false-positive in the sense of having little or no new clinical consequence to the patient," they wrote, adding that this can have a variety of causes: the finding already may be known; may be unchanged over years; may not be treatable in any case; or may be clearly benign at subsequent evaluation.
However, the authors noted that many minor findings can be dismissed at the time of image interpretation—constituting 33.9 percent of all extracardiac findings in the study. With the focused approach, “97.8 percent of these findings were not detected, [and thus] were avoided false-positive findings that might have been generated by a physician not a radiologist who might have been less familiar with the CT appearance of normal variants and inconsequential conditions,” they wrote.
The researchers acknowledged that further quantifying the tradeoff between the greater sensitivity of the broad approach and the lower false-positive rate of the focused approach would require careful cost-benefit analysis.
Johnson and colleagues concluded that the "challenge” presented by extracardiac findings on CCTA images is that a few serious conditions are scattered among a large number of inconsequential ones.
Based on their findings, the authors recommended that any limited viewing approach should include review of the lung window images within the small field of view to detect infiltrates and the occasional pneumothorax.
“The observer also must look for pulmonary emboli, whether or not they are suspected beforehand. Judgment as to which findings to pursue must be made carefully,” wrote the authors, who noted that it sometimes means “taking action and sometimes refraining from action [b]ecause minor findings far outnumber major findings, the ability to differentiate the two will be a crucial factor in determining the overall cost-to-benefit ratio.”