BMJ 2004;329:870-871 (16 October),
doi:10.1136/bmj.329.7471.870
Editorial
Self
monitoring of blood pressure at home
Is
an important adjunct to clinic measurements
Although
measurement of blood pressure in the clinic is said to
be the cornerstone of decision making in hypertension, such
measurements may be unrepresentative of a patient's true
blood pressure because of random fluctuations and
the white coat effect.1-4
In addition, doctors rarely measure blood pressure according
to recommended standards.4
Aimed at improving hypertension management, the 2003
US Joint National Committee recommends the use of self
monitoring of blood pressure before considering the more
expensive, but better validated ambulatory monitoring
of blood pressure.2
Both the Joint National Committee and the 2003 guidelines
from the European Society of Hypertension and the
European Society of Cardiology suggest that self
monitoring might also be used as an alternative to
ambulatory monitoring for the diagnosis of white
coat hypertension.1
2
The 2004 British Hypertension Society guidelines
also acknowledge the increasing use of self monitoring
in clinical practice and provide a threshold level for
the diagnosis of hypertension (more than
135/85 mm Hg).3
In addition, two websites (www.bhs.soc.org
and www.dableducational.org)
provide information on validated devices for self monitoring.
Cross
sectional data and one outcome trial have shown that, as
with ambulatory monitoring, self monitoring
values are lower
than clinic blood pressure measurements.5
6 Self monitoring has several advantages
over clinic measurements—by allowing multiple readings
averaged over time and by taking measurements in
people's usual environment, a more reproducible blood pressure
value is produced that is devoid of the white coat and
placebo effects.4
More importantly, two outcome studies have
shown that
self monitoring predicts cardiovascular outcome better
than
clinic measurements.7
8 Preliminary evidence also shows that self
monitoring may improve control of blood pressure by improving
compliance, as patients become more involved in their
care.9
It has also been suggested that self monitoring might
reduce healthcare costs by reducing the number of
clinic visits.4
Most
self monitoring devices are self activated, and misreporting
of blood pressure readings is possible.4
Recently, the use of memory equipped devices has
reduced such error, which can also be avoided by
adopting telemedicine techniques, which lead to further
improvement in controlling blood pressure.1
Although the technique is easy to learn, some patients
may not be good candidates for self monitoring, which
may result in anxiety or modification of treatment
by the patient.
An
important application of self monitoring is to detect white
coat hypertension.10
Although some have suggested that self monitoring
may represent a cheaper alternative method to detect this
condition, it probably cannot replace ambulatory monitoring.11
12 It can, however, be used as a screening test that
requires confirmation with ambulatory monitoring.10-12
The low cost and wide availability of self monitoring
devices also favour their use as a screening method.
Self monitoring is clearly more appropriate than ambulatory
monitoring for the long term follow up of treated patients
because of its lower cost and greater convenience
for repeated measurements.4
However, ambulatory monitoring is regarded as superior
to self monitoring because it allows for measurements
over a full 24 hour period and has better outcome
data to support its use.4
Recommendations for clinical use4
- Self
monitoring of blood pressure is useful
in detecting white coat hypertension among
patients with persistently raised clinic
blood pressure (on at least three
visits) and no evidence of damage to the target
organ. The diagnosis requires confirmation
with ambulatory monitoring. If self
monitoring is high then treatment should be considered
according to the overall cardiovascular
risk.
- Further
important indications for self monitoring
are improvement of patients' compliance
and long term follow up of patients with hypertension
under treatment
- Self
monitoring should be done by trained patients
under medical supervision. Training should
include information about hypertension,
procedure for self monitoring, advice on
equipment and its proper use, and interpretation
of protocol and data
- Carefully
trained patients can obtain accurate readings
when monitoring themselves by using the
conventional auscultatory technique.
Fully automated memory equipped electronic devices
are preferable because they require less
training, prevent observer and reporting
bias, and allow for average readings over defined
intervals and comparison with previous
periods
- Few
of the devices available on the market
are accurate. Wrist and finger devices
are not recommended. Patients should be warned
that devices for self monitoring are
often put on the market without having
been independently validated. Up to date information
about validated devices is provided
by the website
www.dableducational.org
- The
average of self monitoring measurements
over three to seven days, with duplicate,
seated, morning and evening readings per
day, yields reliable data. Measurements
of the first day should be discarded
because they might not be representative. For
long term observation, measurements
might be repeated for one week every
three months. Overuse of the method and self modification
of treatment should be avoided
-
Average self monitored blood pressure
135/85 mmHg indicates high blood pressure and
<
130/80 mmHg normal blood
pressure. Elevation of self monitored
blood pressure should not in itself be
an indication for drug treatment,
which should be dependent also on the overall
cardiovascular risk profile
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Given
the fallibility of conventional blood pressure measurement,
self monitoring of blood pressure provides supplementary
information to practising doctors enabling a more
precise diagnosis and more accurate titration of
treatment in the long term follow up of hypertension.
George
Stergiou, assistant professor of medicine
Hypertension
Center, Third University Department of Medicine, Sotiria Hospital,
152 Mesogion Avenue, Athens 11527 Greece
Thomas
Mengden, assistant medical director, head of division
Division
of Hypertension and Vascular Medicine, Medizinische Poliklinik,
University Clinic Bonn, Wilhelmstrasse 35, D-5311 Bonn, Germany
Paul
L Padfield, consultant physician
Department
of Medical Sciences, Western General Hospital, Edinburgh EH4
2HU
Gianfranco
Parati, associate professor of medicine
University
of Milano-Bicocca, Cardiology II, S. Luca Hospital, via Spagnoletto,
3, 20149-Milan, Italy
Eoin
O'Brien, professor of cardiovascular pharmacology
ADAPT
Centre and Blood Pressure Unit, Beaumont Hospital and Department
of Clinical Pharmacology, Royal College of Surgeons in Ireland,
Dublin 9, Ireland, (eobrien@iol.ie