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Relative effectiveness of clinic and home blood pressure monitoring compared with ambulatory blood pressure monitoring in diagnosis of hypertension: systematic review

BMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d3621 (Published 24 June 2011) Cite this as: BMJ 2011;342:d3621

Ambulatory blood pressure monitoring for diagnosing hypertension: evidence-based medicine or evidence-based tautology ?

Establishing the diagnosis of hypertension has important
consequences: the subject is labelled as "hypertensive" and a candidate
for lifelong monitoring and treatment. One can only hope that the methods
on which this diagnosis is based are reliable (optimal sensitivity and
specificity), easy to implement on a large scale and cost-effective. There
is over a century's worth of literature on this subject, and even Riva-
Rocci, the inventor of the upper arm blood pressure cuff, mentioned the
problem of white coat hypertension. Three competing methods are currently
in use: the oldest is clinic blood pressure measurement, while ambulatory
blood pressure monitoring (ABPM) and home blood pressure measurement were
introduced more recently. Two recent articles from the same group conclude
that ABPM is the best method, followed by the British NICE guidelines. Is
it deserved?

The first article analysed data from about twenty studies including a
total of 5 683 patients and declared ABPM the winner in terms of
sensitivity and specificity. (1) The second found ABPM the most cost-
effective for diagnosing hypertension in the English primary care setting.
On the same day that the second article was published, the NICE issued
guidelines recommending ABPM as the preferred diagnostic procedure, on the
basis of the two aforementioned articles. (3) The repetition of this
statement, first in the BMJ, then in The Lancet, and finally by the NICE,
should be convincing: ABPM, and only ABPM, is the best tool for diagnosing
hypertension. This is all very well, but this conclusion seems rather
hasty to clinicians who value home measurement.

The conclusion of the first article, which compared the three
measurement methods, was: "Neither clinic nor home measurement had
sufficient sensitivity or specificity to be recommended as a single
diagnostic test. If ambulatory monitoring is taken as the reference
standard, then treatment decisions based on clinic or home blood pressure
alone might result in substantial overdiagnosis". How can three methods be
compared on an impartial basis if the starting premise is that one of them
is the gold standard? The methods section states: "We chose ambulatory
monitoring as the reference standard". Once this choice is made, to
conclude that ABPM is the reference method is a tautology, disguised as
evidence-based medicine. In the discussion section of the article, the
authors admit that they are well aware of the problem: "The findings
clearly depend on the choice of the reference standard".

Is ABPM cheaper than home measurement? The same group published a
demonstration in The Lancet, (2) with results described as "robust", that
ABPM is the more cost-effective method for diagnosing hypertension. Its
higher cost would be offset by savings generated by treating all truly
hypertensive patients and only them. We have two comments. The first is
that sensitivity analyses show that ABPM is not the most cost effective
option if "home monitoring [is] judged as effective as ambulatory
monitoring (a result disputed by recent meta-analysis)." We have just
expressed our concerns with this meta-analysis. Second, by considering
diagnosis in isolation from the patient's subsequent management, the model
disregards the benefits of home measurement during patient follow-up. (4)
If these benefits are taken into account, the cost of home measurement
should not be regarded as a diagnostic cost only, but distributed over the
whole patient's management whenever hypertension is confirmed.

The authors' conclusions that ABPM is the preferred method seem ill
supported to us. We believe it is legitimate not to write off diagnostic
home measurement as hastily as this series of three publications would
suggest. Our views on the role of the various measurement methods may be
influenced by history: clinic measurement remains the method used in
trials, at the request of drug licensing agencies, with the result that
the guidelines do not dare abandon it; solid data is available on ABPM,
and it is considered "the" gold standard for circumventing white coat and
masked hypertension; but so few studies have been conducted on the role of
home measurement in the initial diagnosis of hypertension that its
potential is not clear yet. Time will tell whether the paucity of data is
simply due to the fact that home measurement was introduced more recently
and struggles to find research funding, or whether its intrinsic qualities
and flaws imply that it should not be used as a diagnostic tool.

References

1. Hodgkinson J, Mant J, Martin U, Guo B, Hobbs FD, Deeks JJ, et al.
Relative effectiveness of clinic and home blood pressure monitoring
compared with ambulatory blood pressure monitoring in diagnosis of
hypertension: systematic review. BMJ 2011;342:d3621

2. Lovibond K, Jowett S, Barton P, Caulfield M, Heneghan C, Hobbs FR,
et al. Cost-effectiveness of options for the diagnosis of high blood
pressure pressure in primary care: a modelling study. Lancet 2011;378:1219
-30. Epub 2011 Aug 24

3. Krause T, Lovibond K, Caulfield M, McCormack T, Williams B;
Guideline Development Group. Management of hypertension: summary of NICE
guidance. BMJ 2011; 343:d4891

4. Agarwal R, Bills JE, Hecht TJ, Light RP. Role of home blood
pressure monitoring in overcoming therapeutic inertia and improving
hypertension control: a systematic review and meta-analysis. Hypertension
2011;57:29-38.

Competing interests: No competing interests

07 October 2011
Nicolas Postel-Vinay
MD
Steichen O, Bobrie G.
Hopital Europeen Georges Pompidou. Hypertension Unit. Paris, France