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Effectiveness Review:- Cholesterol: Screening & Treatment

The importance of cholesterol and cholesterol screening in coronary heart disease (CHD) continues to cause controversy in the pages of our most prestigious medical journals. Bandolier is not able to summarise all of that ongoing dispute, but does want to remind its readers of the important Effectiveness Bulletin on "Cholesterol: Screening and Treatment" published by the University of Leeds in June 1993.

The bulletin is short (8 pages), readable and packed with useful information and cogent argument.

Cholesterol as a risk factor

CHD mortality goes up with increasing serum cholesterol. When serum cholesterol rises from 5 to 7.8 mmol/L the age-adjusted 6-year death rate is three times higher than at 5 mmol/L. Cholesterol is only one of a number of independent risk factors, including cigarette smoking, high blood pressure, diabetes, lack of exercise and obesity all of which contribute to CHD.

Is Cholesterol a good measure of risk?

Blood cholesterol by itself is a poor predictor of individual risk of CHD. Data from large studies indicate that there is massive overlap between cholesterol concentrations in individuals who did or did not have a heart attack. Apart from those with very high cholesterol levels an individual's cholesterol value (for 98% of the population) cannot be connected with individual risk of CHD.

Are Cholesterol assays accurate enough?

Over and above the variations in blood cholesterol that occur through the day are superimposed any imprecisions and inaccuracies in the measuring system.

Most hospital biochemistry laboratories do a pretty good job, with levels of accuracy and precision which meet good practice guidelines. Desk-top analysers have a worse reputation, with levels of inaccuracy and imprecision which could mean that a GP would not in reality distinguish confidently between a patient with a value of 7.1 mmol/L (raised) and 5.3 mmol/L (not raised).

Are Cholesterol lowering treatments effective?

Cholesterol lowering is effective in reducing overall mortality in a small group of patients at high overall risk of CHD death. Few people identified purely on the basis of cholesterol levels will benefit from treatment.

A meta analysis which included all randomised controlled single factor trials of cholesterol lowering treatment with at least six months follow up, and in which at least one death occurred showed that treatment was better than no treatment only in those with a very high overall risk of CHD death (>50 deaths per 1000 person years). There was no benefit for those with medium risk (10-50 per 1000); more people with lower CHD risk (<10 per 1000) died taking therapy.



The only people likely to benefit from cholesterol lowering are those with over a 3% chance of dying from a CHD event in the next year. These will have combinations of risk factors, such as men with ischaemic changes, who smoke, have high blood pressure and high cholesterol.

What are the cost implications?

Prescribing of cholesterol lowering drugs in primary care cost £34 million in 1992, and the number of prescriptions is increasing at about 20% per year. The cost per patient is about £400 for both drug treatment and monitoring over one year.

About 120,000 people are estimated to be on treatment, increasing by 27,000 or more each year. The potential for cost escalation is very large, not only because of increases in prescribing, but also because patients may be switched from fibrins to HMG CoA reductase drugs (statins) which are more expensive; the full cost implication of the latter is nearly £20 million a year.

Implications for health care?

Cholesterol screening will not make a contribution to the lowering of overall mortality rates and should be actively discouraged. Therapy should be targeted at those patients with the highest overall CHD risk.



The Health of the Nation target for reduction of CHD by the year 2000 is 40%. Unstructured cholesterol screening and treatment will not be effective in helping to achieve that goal.

Reference:


Effective Health Care. Cholesterol: Screening and Treatment. June 1993. Available from Effective Health Care, 30 Hyde Terrace, Leeds LS2 9LN.


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