Lipid lowering and coronary heart disease risk: how appropriate are the national guidelines?

Abstract

Objective: To assess the effectiveness of current Australian guidelines for prescribing lipid-lowering drugs in identifying high-risk individuals in primary prevention of coronary heart disease.

Design and setting: Coronary heart disease risk profiles were obtained for 280 consecutive patients dispensed lipid-lowering drugs in rural Victoria. Their 10-year absolute risk of coronary heart disease was determined using the Framingham formula. PATIENTS were categorised according to their eligibility for lipid-lowering drugs as defined by current Pharmaceutical Benefits Scheme (PBS) and National Heart Foundation (NHF) guidelines.

Patients: Complete data were available for 230 patients dispensed lipid-lowering drugs. Of these, the 138 patients (60%) with no history of vascular disease are the subjects of our study.

Main outcome measures: Proportion of patients with various 10-year coronary heart disease thresholds (15%, 20% and 30%), compared with their eligibility for lipid-lowering drugs based on Australian PBS and NHF guidelines.

Results: Twenty-six per cent of patients with no history of vascular disease who are currently dispensed lipid-lowering drugs do not fulfil PBS guidelines for treatment. Of patients conforming with PBS guidelines as suitable for lipid-lowering drugs, 39% (95% CI, 30%-49%) had a 10-year risk of coronary heart disease of less than 15%. A similar proportion (41% [95% CI, 32%-50%]) had a 10-year risk of coronary heart disease of less than 15%, but were eligible for lipid-lowering drugs according to NHF guidelines. Adherence to PBS and NHF guidelines in patients currently dispensed lipid-lowering drugs would result in as many as 14% (95% CI, 8%-21%) and 7% (95% CI, 3%-12%) of patients, respectively, not being eligible for treatment, despite having a 10-year risk of coronary heart disease greater than 15%.

Conclusions: Australian guidelines for prescribing of lipid-lowering drugs are poor discriminators of absolute risk of coronary heart disease in primary prevention. Strategies based on the continuous relationship between risk-factor intensity and absolute coronary heart disease risk, such as the Framingham risk estimates, provide a more rational basis for formulating treatment guidelines.