More thoughts on cost-effectiveness
First, I would like to congratulate Marshall on an interesting paper.
I need no further convincing that incremental, rather than average, cost-
effectiveness is the best way to consider the benefits of the more
I have two comments on the paper. The first concerns the impact of
prescription charges, which are paid in the UK by patients under 60 years
old, but not by patients over 60. A prescription charge of £6.30 is more
than the cost of a prescription for a month’s supply of off-patent
diuretics or beta-blockers. Given that the analysis was conducted from the
health service perspective, this means that prescriptions of cheap drugs
to patients under 60 should actually generate income rather than incur
costs. Presumably this would make it spectacularly cost-effective to
prescribe diuretics to all patients under 60, regardless of their
cardiovascular risk, although this really raises the question of whether
the health service perspective was the most appropriate one to take.
My second comment is that the analyses appear to be based on rather a
strong assumption, namely that the relative risk reductions resulting from
treatment are independent of baseline risk. What is the evidence for this?
Trials that have failed to detect differences in relative risk reductions
between high-risk and low-risk groups may simply have lacked the
statistical precision to do so, as detecting statistical interactions of
this kind requires greater statistical power than that required for
detecting main effects of treatment.
The trials of antihypertensive treatment cited in the paper mainly
included patients with hypertension. Do normotensive patients really
derive the same relative benefit from antihypertensive treatment as
hypertensive patients do? If the relative benefits of treatment are less
for patients at lower risk, then the relative cost-effectiveness of
different treatment strategies could change, favouring strategies
targeting high-risk patients.
Competing interests: No competing interests