Volume 200 - Issue 3
Primary prevention of cardiovascular disease: new guidelines, technologies and therapies
Author: Duncan J Campbell
Med J Aust 2014; 200 (3): 146-148. || doi: 10.5694/mja13.10924
Published online: 17 February 2014
Published online: 17 February 2014
Does a formulaic approach based on traditional risk factors measure up?
To the Editor: In describing an approach to primary prevention of cardiovascular disease (CVD) based on 5-year absolute risk, Nelson and Doust acknowledge that this strategy is unlikely to be tested with a randomised controlled trial.1 Yet there are many examples in medicine where guidelines based on good intentions were subsequently shown to be inappropriate when tested in randomised controlled trials. Caution is required in adopting a formulaic approach to primary prevention of CVD, and there is a need for a greater appreciation of the arbitrary way in which CVD risk is categorised and the lack of precision in its estimation.
Australian guidelines categorise a 5-year absolute CVD risk of < 10% as low,1 whereas a much lower threshold of < 6% 10-year risk is advocated in American guidelines.2 Based on Australian guidelines, an individual with 9% 5-year risk of a CVD event will be categorised as low risk. Importantly, the absolute 5-year CVD risk model fails to reflect the trajectory of lifetime risk because significant differences in risk factors at a younger age, when 5-year risk is low, have a dramatic impact on lifetime risk.3
Although validated in an Australian population, the accuracy of prediction of 5-year CVD risk is little better than that of tossing a coin, and the prediction model failed the Hosmer–Lemeshow calibration test.4 Simply repeating blood pressure and lipid level measurements can significantly change the classification of individuals initially classified as intermediate risk.5 Clinicians have an obligation to inform patients of the precision of estimated CVD risk, but how many cardiovascular risk calculators report confidence intervals?
Primary prevention of CVD presents many challenges. It is important that these challenges are recognised and that we do not lull ourselves into a false sense of security that the formulaic approach may offer.
Competing interests
No relevant disclosures.
References
- Nelson MR, Doust JA. Primary prevention of cardiovascular disease: new guidelines, technologies and therapies. Med J Aust 2013; 198: 606-610. CHDHHAIH
- Greenland P, Alpert JS, Beller GA, et al. 2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults: executive summary: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation 2010; 122: 2748-2764. i1142870
- Lloyd-Jones DM, Leip EP, Larson MG, et al. Prediction of lifetime risk for cardiovascular disease by risk factor burden at 50 years of age. Circulation 2006; 113: 791-798. CBBGIIJB
- Zomer E, Owen A, Magliano DJ, et al. Validation of two Framingham cardiovascular risk prediction algorithms in an Australian population: the ‘old’ versus the ‘new’ Framingham equation. Eur J Cardiovasc Prev Rehabil 2011; 18: 115-120. i1142874
- Bell K, Hayen A, McGeechan K, et al. Effects of additional blood pressure and lipid measurements on the prediction of cardiovascular risk. Eur J Prev Cardiol 2012; 19: 1474-1485. i1142878