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· Section 60 Order
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Letters to the Editor
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Statistics
MeReC article was appropriate
From Mrs R. Garnett
Jonathan Bland (PJ, 15 April, p440) suggests that risk reduction figures
should be explicitly clear and differentiated. In his letter, he cited
a recent MeReC Extra article (“NICE appraises statins”, Issue
No. 21, March 2006), where we stated: “Statins are clinically and
cost-effective for people with CHD, significantly reducing cardiovascular
morbidity and mortality by between 20 per cent and 30 per cent.”1
We agree that, where possible, absolute risk reductions (ARR) and related
numbers needed to treat (NNT), as well as relative risk reductions (RRR),
should be stated when reporting clinical data and we always present such
figures in all MeReC publications.
In the MeReC Extra article cited, it was appropriate for us to present
the RRR figures of 20 per cent to 30 per cent for cardiovascular morbidity
and mortality with statins in secondary prevention. With hindsight, we
could have made it more explicitly clear that this was an RRR, not an
ARR. However, the relative risk figures quoted came from a meta-analysis
carried out for the National Institute of Health and Clinical Excellence
statin appraisal, which, correctly, did not give absolute risk figures.
In a meta-analysis, pooled data from several trials are presented as
relative risks. To generate ARRs and related NNTs from pooled data is
problematic as the baseline risk of patients will vary from trial to
trial depending on patient characteristics, clinical setting etc, and
trials may be of varying length.2
In order to present the more meaningful absolute reductions in cardiovascular
morbidity and mortality with statins in secondary prevention, both the
NICE technology appraisal and the MeReC Extra article quoted separate
NNTs from the three largest statin trials in people with coronary heart
disease. The MeReC Extra article stated: “In the three largest
trials of people with CHD, the NNTs to prevent one CHD death or non-fatal
myocardial infarction over five to six years were 12, 29 and 34.”1
This sentence directly followed our statement about relative risk reductions,
and for Mr Bland to imply that we only quoted relative reductions is,
therefore, misleading.
Through our presentation of both relative and absolute figures, MeReC
readers are informed of the impact of statins both on a population level
and on an individual patient level, an issue which is at the crux of
the debate about when it is appropriate to initiate statin therapy.
Ruth Garnett
Assistant Director
MeReC Publications
References
1. National Institute for Health and Clinical Excellence. Statins for
the prevention of cardiovascular events. Technology appraisal 94. London:
NICE; January 2006.
2. Smeeth L, Haines A, Ebrahim S. Numbers needed to treat derived from
meta-analyses — sometimes informative, usually misleading. BMJ
1999;318:1548–51.
Make ARR figures available
From Mr G. Roberts, MRPharmS
I would like to add my full support to Jonathan
Bland’s request
(PJ, 15 April, p440) for the publication of absolute risk reduction (ARR)
figures for all studies reported in The Pharmaceutical Journal. We have
all seen the problems of quoting relative risk reduction (RRR) figures,
for example, in the reporting during the mid 1990s of the increased risk
of breast cancer in women taking certain oral contraceptives.
Most patients will be able to appreciate the concept of the number needed
to treat (NNT). Publishing these figures in the PJ will allow pharmacists
to provide patients with information about benefits and risks in a form
that is consistent and easy to understand. If a study does not quote
an ARR, then we should wonder why this is so.
Gary Roberts
Royal Darwin Hospital
Darwin, Australia
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In our reports of clinical trials data we try to include ARR figures
when they are available. When they are not available, the news team
makes a decision on whether the data as they stand are of value to pharmacists.
— EDITOR
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The
Pharmaceutical Journal