Substantially different scoring on coronary artery calcification produced by CT scanners from four different vendors could affect the medical treatment chosen by doctors for up to 6.5 percent of patients, according to a study published online August 22 of Radiology.

Researchers Martin J. Willemink, MD, of Utrecht University Medical Center in the Netherlands, and colleagues wrote that because of these scoring differences, patients with intermediate risk could be reclassified to high or low risk of heart disease, prompting doctors to change their treatment.

“[O]ur multivendor study showed that coronary calcium scoring by using different state-of-the-art CT systems from four different vendors resulted in substantially different Agatston scores, which can result in substantial reclassification of cardiovascular risk and changes in treatment,” they wrote.

“Given the large population at intermediate risk, the absolute number of reclassifications can be substantial.”

Treatment of coronary heart disease depends on classification of risk. Those patients classified as high risk, for example, are often treated with medication to lower blood pressure and to lower cholesterol.

The American Heart Association recommends measurement of coronary calcium expressed as Agatston scores in asymptomatic adults at intermediate and low-to-intermediate risk, who make up about 40 percent of the U. S. adult population, the authors noted.

Researchers scanned 15 ex vivo human hearts with scanners from four different vendors (Philips, Toshiba, GE and Siemens) to analyze the differences in Agatston scores. Using these results, they simulated the effects of Agatston score differences on risk reclassification of 432 participants at intermediate risk from the Rotterdam Study.

The Agatston scores obtained by using systems from different vendors were compared for each heart, they said. Only one of the hearts did not have calcification. Median Agatston scores ranged from 332 to 469.

“To the best of our knowledge, this is the first study in which the differences in coronary calcium scoring between the state-of-the-art CT systems from all major vendors were analyzed,” they commented.

Researchers noted that although a consensus standard had been developed for Agatston score quantification with older CT scanners, the major vendors all have introduced new CT systems and updated software.