International Task Force for Prevention of
Coronary Heart Disease
CORONARY HEART DISEASE: REDUCING THE RISK
2. The assessment of global risk
To provide an appropriate level of treatment for each risk factor, an essential first step is to judge the patient's level of CHD risk. While this is now generally accepted, the proposed methods diverge widely. Many attempts to quantify this assessment have been inconsistent and incomplete:
For these reasons, efforts have been made in recent years to use data from prospective epidemiological studies such as the Framingham Study or the Münster Heart Study (PROCAM) to identify independent CHD risk factors and to assess their relative importance by means of mathematical modelling. In the Framingham and Münster Heart studies, this approach has led to the development of mathematical algorithms for the prediction of risk. The Framingham algorithm for prediction of first events in men includes the independent variables age, total cholesterol/HDL-cholesterol ratio, systolic blood pressure, left ventricular hypertrophy, diabetes mellitus, and smoking 6. The PROCAM algorithm was also designed for the prediction of first event and takes into account the nine independent risk variables: age, smoking history, personal history of angina pectoris, presence or absence of a family history of MI, systolic blood pressure, LDL-cholesterol, HDL-cholesterol, triglyceride, and the presence or absence of diabetes. These risk factors are dealt with in turn in the section that follows. The PROCAM algorithm will discriminate risk over a wide range; persons in the upper and persons in the lower quintile of the risk algorithm differ by 40-fold in their level of risk (Figure 2). Additional risk factors such as elevated levels of fibrinogen or Lp(a), though not yet incorporated into this algorithm, also assist in risk stratification. The algorithm has also been used to develop the Risk Calculator (available in interactive form on the Task Force website at http://www.chd-taskforce.com) which can be used to quantify a person's risk of suffering a coronary event.
Figure 2: Estimated risk of a coronary event among men aged 35 to 65 years in the Münster Heart Study, expressed as quintiles of the PROCAM multiple logistic function.
An alternative approach that works well in practice is to forego quantitative assessment of risk and to use; instead, clinical judgement to integrate all the relevant information concering risk status, i.e. age, sex and menopausal phase, the number of risk factors and, importantly, their severity. This approach is common in clinical assessments. The greater the risk , the lower will be the target value for LDL-cholesterol concentration, and the more vigorous the treatment required. But, as shown in Sections Fehler! Verweisquelle konnte nicht gefunden werden. (Grades of increased risk) and 3.4.2 (Target levels for lipid-lowering therapy), the practical requirement is simply to assign the patient to one of a small number of grades of risk.
Previous rigid systems of risk classification have attempted quantitative risk assessment from a small number of the many risk factors, often simply dichotomised as present or absent without consideration of their severity. Such approaches can be abused to conceal economic considerations, i.e. the need to constrain the use of drug therapy. It is true that even in wealthy countries, the therapeutic possibilities made available by medical research and development have caused demand to outstrip available funding. One consequence has been efforts to limit reimbursement of lipid-lowering therapy. While this is understandable, it should be clearly stated as such; economic issues are better dealt with independently of purely clinical matters, and should not be conflated with them.
In any case, the treatment options for hyperlipidaemia are not merely whether or not to use a lipid-lowering drug. Dietary treatment varies widely in the degree of change recommended. Drug treatment may be conventional monotherapy, or may require a drug combination, or in patients who are incompletely responsive to diet, a very low dose of a lipid-lowering drug will often suffice to achieve fully satisfactory control. Thus there is a wide range of therapeutic possibilities.