New ACC/AHA CV-Risk Calculator Hits Europeans Twice as Hard

March 04, 2014

LAUSANNE, SWITZERLAND — On two continents now, the controversial calculator of 10-year cardiovascular risk introduced last year in a new set of guidelines from the AHA and ACC classifies an unprecedented—some say excessive—proportion of the population as at enough risk to recommend statin therapy. Were the guidelines fully applied to a European population, say researchers here, it would not only balloon the number of persons considered at high CV-disease risk for whom statins would be considered appropriate, it would more than double the societal cost of daily statin therapy for primary prevention of cardiovascular disease[1].

European researchers found that compared with using European Society of Cardiology (ESC) guidelines, application of the risk calculator and statin recommendations in the ACC/AHA guidelines to the Swiss population doubled the estimated proportions of both men and women to whom statins would be offered, with a vastly pronounced effect in the youngest age group, those 50 to 60 years of age.

As to why the ACC/AHA standards work on the Swiss population so much differently than the ESC guidelines, the authors propose that it "may be due to differences in the prevalence of CV risk factors between the US and Europe."

For example, "HDL-cholesterol levels are relatively high in Switzerland, which might partly explain the lower risk," speculated coauthor Dr Pedro Marques-Vidal (Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland) for heartwire in an email. The protective effect of HDL cholesterol is strongly represented in the European equations, he said.

"Cardiovascular-disease incidence and mortality vary quite a lot in Europe, so our results cannot be directly applied to other countries, as their risk-factor levels are different," he noted. Moreover, "Our study included mainly subjects of [European] origin, so our findings might not apply to more ethnically diverse populations." He said research teams elsewhere in Europe are likely conducting similar analyses on other local populations.

The new North American guidelines, including the 2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk and the 2013 ACC/AHA Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults , wereunveiled in November, 2013 and covered by heartwire at the time. Almost right away, they were very publicly criticized for their reliance on a risk calculator derived from cohorts said not to be representative of contemporary practice and for steering away from familiar LDL-cholesterol targets to guide statin therapy, among other reasons.

The new analysis, with first author Dr Julien Vaucher (Centre Hospitalier Universitaire Vaudois), was published online February 25, 2014 in the European Heart Journal. Vaucher et al derived 10 cardiovascular-disease risks based on separate application of the Swiss SCORE risk criteria used in the ESC guidelines and the new ACC/AHA atherosclerotic cardiovascular risk equations to a cohort of patients aged 50 to 75 years from the population-based Swiss CoLaus study. Both results were extrapolated to the full Swiss population of the same age group.

Ratio, Population at Risk by ACC/AHA vs ESC Guidelines Criteria, and Estimated Daily Cost of Resulting Statin Therapy in the Population of Switzerland

Age (y) Men Womena Total Daily costb
50–60 30.6 33.2 447
60–70 2.1 5.8 2.5 884
70–75 1.0 1.1 1.1 572
All 2.2 1.9 2.1 2023

a. SCORE equation doesn't predict CV risk for women under 60 years
b. Cost of atorvastatin expressed in 1000s of Swiss francs

Both the number of people at risk and the estimated daily cost of statin therapy for 50- to 60-year-olds using ESC risk criteria were only 3% of the corresponding number and cost using ACC/AHA criteria. Put another way, 30 times as many men in that age group were at risk when the ACC/AHA criteria were applied.

The excesses using ACC/AHA criteria were elevated but less pronounced for those 60 to 70 years old: twice as many men and about six times as many women were at risk within that age group. Similar numbers of men and women aged 70 to 75 were at risk using the two sets of criteria.

In their report published under the heading Current Opinion, the group recommends further studies "to validate the new ACC/AHA risk equation and to assess the cost-effectiveness of the ACC/AHA guidelines in non-US countries." Marques-Vidal acknowledged for heartwire that, regardless, it's unlikely the ESC would switch from using the SCORE equations to those used by the ACC/AHA guidelines.

Neither Marques-Vidal nor Vaucher declared conflicts of interest. Disclosures for the  coauthors are listed in the paper.

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