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Economics
The burden of CHD as a percentage of healthcare expenditure has been estimated to be approximately 2.6% in Germany, 7.9% in the USA and 1% in the UK. Direct costs of CHD are primarily due to hospitalisation, whereas productivity losses are the main component of indirect costs. It is important to note that the management of dyslipidaemia and of other risk factors has led to a substantial reduction of fatal and nonfatal CHD.
Analysing drug costs
In pharmaco-economic research, a drug is analysed in terms of input-to-output
costs. Input costs include diagnosis, treatment and management of the
disease plus the associated costs of treating side effects. Output costs
include not only healthcare savings, but also changes in health status
[Szucs, 1998].
Instruments for measuring costs
The most used instrument in pharmaco-economic research is the cost-effectiveness analysis, which measures differences in the cost of treatments in outcome units such as actual lives saved (see below). It is particularly useful when comparing alternative therapies having the same outcome units, but not the same effectiveness. The cost of therapy divided by the units of effectiveness gives a value that allows a drug to be compared and where a lower number indicates a more cost-effective outcome.
The most used outcome units to evaluate lipid-lowering treatments are:
- cost per year of life saved (YOLS), which requires a calculation of life expectancy; and
- cost per quality-adjusted life-year (QALY) gained. QALY is calculated by adjusting
the length of time affected by a certain disease for the utility value
(on a scale 0-1) of the resulting health status [Szucs,
1998].
Costs in the USA and UK
It is evident that the higher the level of CHD risk, the lower the cost
per YOLS. In turn, CHD risk is related to age, gender and other classical
risk factors, including cholesterol levels. Considering, for instance,
the lifetime risk of death 10 years after a myocardial infarction in males
in the Framingham Study, pravastatin treatment in patients with CHD with
one risk factor is associated with a cost per YOLS of US$12,665, with
two risk factors US$9368 and with three risk factors US$7124 [Szucs,
1998]. In the UK, the cost of 10-year survival with statin treatment
for a middle-aged patient with CHD and a serum cholesterol level greater
than 5.4 mmol/L (208 mg/dL) would be GB£32,000 per YOLS, but it would
be GB£136,000 per YOLS for a middle-aged man with no history of CHD and
a cholesterol level greater than 6.5 mmol/L (250 mg/dL) and GB£361,000
per YOLS for a perimenopausal woman with angina and a cholesterol level
between 5.5 and 6.0 mmol/L (212 and 231 mg/dL) [Szucs,
1998].
Costs in a secondary prevention study: 4S
An obvious limitation of the above cost estimates is that they are focused
on mortality and ignore the benefits and the costs related to nonfatal
complications of CHD. An example of this observation can be found in the
secondary prevention from the Scandinavian Simvastatin Survival Study
(4S). Treatment with simvastatin for five years in 59-year-old women with
CHD and a cholesterol level 6.75 mmol/L (261 mg/dL) would cost US$10,300
per YOLS if considering only direct costs, but would cost only US$4900
if considering indirect and direct costs [Johannesson,
1997].
Costs in primary prevention studies: WOSCOPS and CARE
Much more debatable is the issue of cost-effectiveness analysis of lipid-lowering
therapy (which can be identified today with statins) in the setting of
primary prevention. In the West of Scotland Coronary Prevention Study
(WOSCOPS) the cost of a lifelong discounted treatment with pravastatin
in the UK in those with a risk of CHD events of 1.5% per year would be
GB£18,200 per YOLS, for those with a risk of 2% per year GB£15,600, for
those with a risk of 3% per year GB£12,000 and for those with a risk of
4.5% per year only GB£7400 [Pickin, 1999]. These calculations are based
on the evidence that the relative risk reduction with statin treatment
remains approximately constant, provided that the LDL-C level is above
3.2 mmol/L (123 mg/dL; the level of baseline LDL-C in the Cholesterol
and Recurrent Events [CARE] study below which apparently no benefit was
observed in the pravastatin group) [Pickin,
1999]. As a consequence, the absolute benefit from treatment is determined
by the absolute CHD risk; that is, therefore, a major determinant of the
cost-effectiveness analysis of statin treatment. Accordingly, it is not
surprising that in the USA, in older patients (75-84 years of age) with
myocardial infarction, statin treatment cost per QALY can be as little
as US$5400.
Which criterion should be used to establish the
cost-effectiveness of a drug?
One method is to use as a reference an average of 500 life-saving interventions,
from air bags to pollution control. Another method is to use as a reference
the cost of the life-saving interventions that are more used or recommended:
according to this last method, the thresholds of cost-effectiveness
per QALY for primary and secondary prevention are US$70,000 and US$14,000,
respectively. In Europe, however, there is a general agreement to consider
statin treatment as cost-effective in patients with CHD risk higher
than 2% per year (3% in the UK) [Pickin, 1999;
Shepherd, 2001].
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