Proposed Joint British Societies Cardiovascular Disease


The recent NICE guidance on lipid management [1] endorses the JBS2 recommendations [2] in advocating a cardiovascular disease (CVD) risk threshold of 20% over the next 10 years as an indication for the introduction of statin therapy. Both NICE and JBS2 also recommend that CVD risk is estimated using epidemiological data such as those generated from the Framingham Study as an aid to clinical judgment. They differ, however, in that NICE proposes that the upper age limit at which CVD risk is estimated in this way is extended to 75 years rather than the 70 years in JBS2. This has left many clinicians and nurses without a readily available means of assessing risk in these older people. The figures below show new charts which are revised to permit this.

The revised charts differ from the JBS2 version in omitting the line showing 30% 10 year risk which is now superseded as a threshold for statin use. The new charts also recognise that there is a small group of non-smoking men aged 50-59 years with low systolic and diastolic blood pressure and a low total serum cholesterol to HDL ratio whose CVD risk is less than 10% (green). This lack of recognition of their evident cardiovascular health in the earlier charts, although it would not lead to them receiving statin, might be discouraging to their maintenance of a healthy lifestyle. Furthermore, the distinction between 10% and 20% risk could become clinically more important if future statin indications become more liberal to take into account new clinical trial evidence.

It should also be noted that NICE lays more emphasis on an adverse family of CVD than JBS2. It recommends that, if early-onset CVD has occurred in a first degree relative (male aged less than 55 years or female aged less than 65yers) risk should be increased 1.5 times and that it should be doubled if more than one first degree relative has such a history.

REFERENCES

1.         National Institute of Health and Clinical Excellence Lipid Modification: Cardiovascular risk assessment and the modifications of blood lipids for the primary and secondary prevention of cardiovascular disease. Full Guidelines London: National Collaborating Centre for Primary Care May 2008
2.        Wood, D.A., Wray, R., Poulter, N., Williams, B., Kirby, M., Patel, V. et al JBS2: Joint British guidelines on prevention of cardiovascular disease in clinical practice. Heart 2005; 91(Suppl V): V1-52.

nondiabetic_men.jpg

 

nondiabetic_women.jpg

Cardiovascular Disease Risk Prediction Chart reproduced with permission from The University of Manchester Department of Medical Illustration, Manchester Infirmary

How to use the Cardiovascular Disease Risk Prediction Charts for Primary Prevention
These charts are for estimating cardiovascular disease (CVD) risk (non-fatal myocardial infarction [MI] and stroke, coronary and stroke death and new angina pectoris) for individuals who have not already developed coronary heart disease (CHD) or other major atherosclerotic disease. They are an aid to making clinical decisions about how intensively to intervene on lifestyle and whether to use antihypertensive, lipid lowering medication and aspirin.

  • The use of these charts is not appropriate for the following patients groups. Those with:         

• CHD or other major atherosclerotic disease         
• Familial hypercholesterolaemia or other inherited dyslipidaemias         
• Chronic renal dysfunction         
• Type 1 and 2 diabetes mellitus

  • The charts should not be used to decide whether to introduce antihypertensive medication when blood pressure (BP) is persistently at or above 160/100 or when target organ damage (TOD) due to hypertension is present. In both cases antihypertensive medication is recommended regardless of CVD risk. Similarly the charts should not be used to decide whether to introduce lipid-lowering medication when the ratio of serum total to high density lipoprotein (HDL) cholesterol exceeds 7. Such medication is generally then indicated regardless of estimated CVD risk.
     
  • To estimate an individual's absolute 10 year risk of developing CVD choose the table for his or her gender, smoking status (smoker/non-smoker) and age. Within this square define the level of risk according to the point where the coordinates for systolic blood pressure (SBP) and the ratio of total cholesterol to HDL-cholesterol meet. If no HDL cholesterol result is available, then assume this is 1.00mmol/l and the lipid scale can be used for total serum cholesterol alone.
     
  • Higher risk individuals (red areas) are defined as those whose 10 year CVD risk exceeds 20%, which is approximately equivalent to the CHD risk of >15% over the same period indicated by the previous version of these charts.
     
  • The chart also assists in the identification of individuals whose 10 year CVD risk moderately increased in the range 10-20% (orange area) and those in whom risk is lower than 10% over 10 years (green area).
     
  • Smoking status should reflect lifetime exposure to tobacco and not simply tobacco use at the time of assessment. For example, those who have given up smoking within 5 years should be regarded as current smokers for the purposes of the charts.
     
  • The initial BP and the first random (non-fasting) total cholesterol and HDL cholesterol can be used to estimate an individual's risk.
    However, the decision on using drug therapy should generally be based on repeat risk factor measurements over a period of time.
     
  • Men and women do not reach the level of risk predicted by the charts for the three age bands until they reach the ages 49, 59, and 69 years respectively. The charts will overestimate current risk most in the under forties. Clinical judgement must be exercised in deciding on treatment in younger patients. However, it should be recognised that BP and cholesterol tend to rise most and HDL cholesterol to decline most in younger people already possessing adverse levels. Thus untreated, their risk at the age 49 years is likely to be higher than the projected risk shown on the age-less-than 50 years chart.
     
  • These charts (and all other currently available methods of CVD risk prediction) are based on groups of people with untreated levels of BP, total cholesterol and HDL cholesterol. In patients already receiving antihypertensive therapy in whom the decision is to be made about whether to introduce lipid-lowering medication or vice versa the charts can act as a guide, but unless recent pre-treatment risk factor values are available it is generally safest to assume that CVD risk is higher than that predicted by current levels of BP or lipids on treatment.
     
  • CVD risk is also higher than indicated in the charts for:-

    Those with a family history of premature CVD or stroke   (male first degree relatives  aged
    Those with raised triglyceride levels
    Women with premature menopause
    Those who are not yet diabetic, but have impaired fasting glucose (6.1-6.9mmol/l)
                             
  • In some ethnic minorities the risk charts underestimate CVD risk, because they have not been validated in these populations. For example, in people originating from the Indian subcontinent it is safest to assume that the CVD risk is higher than predicted from the charts (1.5 times).
     
  • The charts may be used to illustrate the direction of impact of risk factor intervention on estimated level of CVD risk. However, such estimates are crude and are not based on randomised trial evidence. Nevertheless, this approach maybe helpful in motivating appropriate intervention. The charts are primarily to assist in directing intervention to those who typically stand to benefit most.