International guidelines on coronary artery calcium (CAC) scoring all suggest the tool has value, but otherwise agree on little else, an Australian-led review has found.

A team of cardiologists from Melbourne compared recommendations from CSANZ, the ACC/AHA and the ESC, finding significant disagreement on eligibility thresholds, pharmacological management and repeat testing. Writing in the Internal Medicine Journal [link here], they warned the gaps “may contribute to clinical uncertainty and inconsistent implementation.”

Who qualifies for CAC scoring?

All three bodies agreed CAC scoring suits asymptomatic individuals at intermediate cardiovascular risk, but defined “intermediate risk” differently, found Royal Melbourne Hospital cardiologist Dr Anoop Koshy and colleagues.

• CSANZ uses a 5-year absolute cardiovascular risk of 10–15%, derived from the NVDPA tool
• ACC/AHA uses 10-year ASCVD risk
• ESC uses comorbidities such as CKD or diabetes as risk markers

These differences had real clinical consequences. A 55-year-old patient with diabetes could qualify for CAC testing under European criteria but not under Australian or US guidelines, depending on how risk scores were calculated, the authors noted. They called for “harmonisation or at the very least explicit translation of international thresholds into the Australian risk framework.”

What to do with the result?

How CAC scores should influence clinical decision-making also differed across frameworks, the review found.

In the ACC/AHA framework, a CAC score could “de-risk” patients with borderline 5–7.5% ASCVD risk or “re-risk” those at intermediate risk. Under CSANZ guidance, a score of 0 warranted deferral of therapy, while a score above 400 signalled a need for aggressive treatment.

On pharmacotherapy, the ACC/AHA and CSANZ both recommended statins for CAC scores of 100 or above, or above the 75th percentile. CSANZ also recommended aspirin, a notable divergence given the broader move away from aspirin in primary prevention due to bleeding risk.

The authors attributed the variation partly to each jurisdiction using different risk calculators. Overall, the discrepancies reflected “the absence of definitive evidence” on CAC-guided decision-making, they argued.

“Only with a stronger evidence base can meaningful guideline alignment be achieved,” the team concluded, noting that CAC scoring in Australian clinical practice remained “poorly defined,” with limited public funding constraining its uptake.