Editorial

Self monitoring of blood pressure at home

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

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