Review: Limited role for ambulatory and self-measurement devices in the diagnosis and management of hypertension
ACP J Club.1993 Nov-Dec;119:78. doi:10.7326/ACPJC-1993-119-3-078
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Appel LJ, Stason WB. Ambulatory blood pressure monitoring and blood pressure self-measurement in the diagnosis and management of hypertension. Ann Intern Med. 1993 Jun 1;118:867-82.
To review the use of ambulatory and self-measurement devices in the diagnosis and management of hypertension.
Relevant citations were identified by searching MEDLINE from 1966 to early 1992 using the MeSH headings “blood pressure determination” and “blood pressure monitoring.” Articles published before 1966 were identified from reference sections of other papers.
Articles selected for detailed review were original research studies pertaining to the diagnosis, treatment, or prognosis of hypertension using self-measured blood pressure (BP), noninvasive ambulatory BP monitoring (ABPM), and measurements by nonphysicians.
Data on the BP measurement techniques used, BP levels by different techniques, relation between end-organ damage and BP, prediction of cardiovascular mortality and morbidity, use of ambulatory and self-measured BP during treatment, and safety were extracted.
A meta-analysis was not done because of heterogeneity in study designs and the small number of prospective data. The accuracy and reliability of measurement was problematic with all 3 techniques. Studies that compared all 3 measurement techniques found office BP measurements to be higher than both self-measured BP and daytime or 24-hour ABPM (the latter because of nocturnal BP decline). Most studies (all cross-sectional) that have examined associations between left ventricular hypertrophy and BP found stronger correlations with ABPM than with office BP readings. The single prospective study on ABPM and clinically evident cardiovascular events found that ABPM was superior to office BP measurements, but the study has been criticized on methodologic grounds. Only 1 of 5 clinical trials testing self-measured BP, used alone or combined with other strategies, showed a statistical improvement in medication adherence and BP control. The risks associated with noninvasive ABPM were minor but the cost of ABPM may be considerable.
A review of recent evidence suggests a limited clinical role for ambulatory and self-measurement devices in the diagnosis and management of hypertension.
Sources of funding: Johns Hopkins University School of Medicine; National Heart, Lung, and Blood Institute; Pew Charitable Trust; Rockefeller Foundation.
For article reprint: Dr. L. Appel, Welch Center for Prevention, Epidemiology & Clinical Research, The Johns Hopkins Hospital, Carnegie 291, 600 North Wolfe Street, Baltimore, MD 21287-6231, USA. FAX 410-955-0476.
Self-measurement devices will continue to proliferate, more so if reimbursement is provided. Why? Because office BP measurements provide only a tiny window on the 9 million heartbeats between prescription refills, because many patients want to measure their own BP, and because problems of accuracy, reliability, and prognostic validity can be resolved.
Considerable epidemiologic evidence supports decision making by the use of office BP measurements. Or does it? BP readings taken in major trials do not necessarily equate with casual recordings. Differences may result from observer competence, equipment accuracy, number of measurements, cuff sizes, sitting compared with supine positioning, resting period, short-term effects of coffee and cigarettes, and "white coat" effects.
The 1992 Association for the Advancement of Medical Instrumentation (AAMI) guidelines (1) should ensure accuracy and, perhaps, reliability of new devices, but not of existing devices in the United States. AAMI and British Hypertension Society guidelines are demanding, requiring 255 paired comparisons against trained observers with sphygmomanometers in 85 patients with widely ranging BPs. The devices used in pharmacies and supermarkets and the inexpensive, over-the-counter devices have not been shown to meet these standards.
"Ambulatory" devices are essentially research tools—or at least for experienced users. True ambulatory BP readings are impossible to obtain noninvasively because of motion artifact. The devices are costly, drain time, and need close technical and computing support. The learning curves are lengthy.
BP recording outside the office nonetheless may be useful in selected patients—those with seemingly unrepresentative office BP readings, apparent drug resistance, and, occasionally, in suspected episodic hypertension or hypotension. How should BP be measured? The mercury sphygmomanometer is the gold standard and should be used, if possible, for home and work assessments. Nonmercury devices should be used only if they are known to meet agreed standards for accuracy and repeatability of readings.
Michael J. Jamieson, MD
University of Texas Health Science CenterSan Antonio, Texas, USA