A coronary artery calcium (CAC) score of 100 is a suitable and cost effective threshold for initiating statin treatment in patients at low to intermediate CVD risk based on conventional risk scores.
A study, published in the MJA [link here], said systematic CAC assessment was cost effective if statin therapy was initiated in people with baseline Australian absolute cardiovascular disease risk (ACVDR) risk of at least 5% and CAC scores of ≥100.
The study modelled the relative cost-effectiveness of a CAC score-guided approach to statin eligibility compared to current Australian and American College of Cardiology/American Heart Association (ACC/AHA) guidelines in a sample of 1,083 patients with family histories of premature coronary artery disease but no symptomatic cardiovascular disease.
It found statin therapy would be recommended in 7.1% of patients using Australian guidelines and a 5-year CVD risk ≥ 10%.
With ACVDR 5-year risk ≥ 2% and CAC score > 0 as the criteria, 45.8% would be eligible and with ACVDR 5-year risk ≥ 2% and CAC score ≥ 100, 14.3% would be eligible for statins.
According to ACC/AHA guidelines, and a 10-year pooled cohort equation risk ≥ 7.5%, 24.6% of people were eligible for statins.
CAC-guided strategies increased the mean cost to the Australian health care system by $493 per person with CAC score > 0 as the criterion and by $289 with CAC score ≥ 100 as the criterion.
The study said the CAC score > 0 criterion would prevent 267 deaths and 795 symptomatic cardiovascular events, “achieving a mean increase of 0.0093 (95% CI, 0.0074–0.0112) QALYs per person at a mean ICER of $53 028 per QALY gained.”
“With CAC score ≥ 100 as the criterion, 163 deaths and 330 symptomatic cardiovascular events were averted, achieving a mean increase of 0.0087 QALYs per person at an ICER of $33 108 per QALY gained,” the study said.
“The mean cost of applying the American guidelines was also higher than applying the Australian guidelines (+$92 per person; 95% CI, $81–103 per person), but did not increase utility.”
“A strategy based on CAC scores ≥ 100 was cost-effective if the baseline 5-year ACVDR risk was at least 5%.”
The investigators, including cardiologists Professors Tony Stanton, Stephen Nicholls, Andrew Tonkin, Gerald Watts and Thomas Marwick, said their findings support CSANZ and NHF position statements on CAC scoring.
“Nevertheless, traditional risk factors retain their independent predictive value, and statin treatment is appropriate for people with low CAC scores but at higher baseline risk,” they said.
They noted that cost-effectiveness for the CAC-guided strategy was dependent on statin initiation and discontinuation rates but that “CAC scoring may motivate clinicians to initiate and patients to adhere to statin therapy.”
“Incorporating non-traditional risk factors and refining criteria for statin treatment should be considered when revising primary CVD prevention guidelines in Australia,” they concluded.