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Is self monitoring of blood pressure in pregnancy safe and effective?

BMJ 2014; 349 doi: https://doi.org/10.1136/bmj.g6616 (Published 18 November 2014) Cite this as: BMJ 2014;349:g6616

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Home Blood Pressure Measurements. Pros and cons

According to the Global Burden of Disease Study 2010 hypertension is the most important preventable cause of morbidity and mortality globally, affecting over 1 billion people.1 In Europe the prevalence of hypertension appears to be around 30–45% of the general population, with a steep increase with ageing.2 Furthermore, as a recent multinational study has shown, significant proportions of people are either unaware or have poor control of their elevated blood pressure (BP).3 Although the conventional office blood pressure (CBP) has been the cornerstone for hypertension diagnosis and management for decades, it is now recognized that, for the reliable evaluation of elevated BP, evaluation using 24-hour ambulatory (ABPM) or self-home BP monitoring (HBPM) is often required.2,4 Much evidence has accumulated that shows that HBP can predict hypertensive target-organ damage more effectively than CBP.5,6 Furthermore, several outcome studies demonstrated the prognostic value of HBPM for cardiovascular disease to be superior to that of CBP.6-8 HBP also seems to substantially refine risk stratification at CBP levels assumed to carry no or only mildly increased risk, in particular in the presence of masked hypertension.9

1. Diagnosis of hypertension
According to the ESH/ESC guidelines CBP currently remains the ‘gold standard’ for screening, and diagnosis of hypertension.2 However, out-of-office BP (HBPM and ABPM) is an important adjunct to conventional office BP measurement, especially when there is suspicion of white-coat, and masked hypertension.2 Several cross-sectional studies investigated the diagnostic performance of HBPM by taking ABPM as the reference method.10,11 There is considerable agreement between the two methods, with high specificity and negative predictive value (>80%) and lower sensitivity and positive predictive value (60–70%).11 This accruing evidence led both European and United States guidelines to emphasize the importance of HBPM in the diagnosis of hypertension.2,12 In Japan, HBPM is actually the preferred method for the diagnosis (and treatment) of hypertension.13 Although HBPM might be appropriate for the initial diagnostic evaluation of most cases with elevated BP (in primary care), ABPM if available might be more suitable when an unbiased evaluation is required within 24 hours (in specialist care).2,11 Furthermore, ABPM has the advantage of assessing BP variability and dipping status.4 However, HBPM can provide data on the short-term variability of BP14 and is also an excellent way to detect long-term variations in BP, including seasonal variations.15 A recent systematic review showed that preliminary data indicate an important and independent role of day-by-day HBP variability in the pathogenesis of hypertension induced cardiovascular damage.16 Furthermore, nowadays there are HBPM devices which allow nocturnal monitoring and have good agreement with ABPM in detecting non-dippers.17 HBPM during sleep as well as morning and evening HBP over a long period might provide reliable information on the nocturnal dipping status.13

2. Treatment of hypertension and long-term follow-up
Self-monitoring of hypertension is now common, with more than a third and up to two thirds of patients using it.18-20 Guidelines in Europe,21 the United States,22 and Japan23 recommend that HBPM should be offered to all patients with elevated BP, whereas ABPM monitoring should be offered in selected cases. A systematic review of 72 randomized controlled trials (RCT) that evaluated the effectiveness of several interventions (self-monitoring, educational interventions directed to the patient, educational interventions directed to the health professional, health professional-led care, organizational interventions that aimed to improve the delivery of care, and appointment reminder systems) aiming to improve BP control showed HBPM to be the most effective method.24 Furthermore, treated hypertensive patients who perform HBPM might have better long-term adherence to pharmacotherapy.25 Recent systematic reviews of RCT investigating self-monitoring have shown promise in the reduction of BP and higher hypertension control rates particularly when combined with other interventions, like tele-monitoring.26-29

3. Limitations of home blood pressure monitoring
The ESH Working Group on Blood Pressure Monitoring has proposed a number of recommendations for HBPM.21,30 It is imperative to follow these recommendations (avoid devices worn on the wrist; using accurate, independently validated devices; using 3–7 days with duplicate morning and evening measurements and discard the first day; objective reporting using automated memory or PC link; telemonitoring) in order for the HBPM to be trustworthy and meaningful.30 Only then can one avoid what is the biggest limitation of HBPM; the fact that hypertensive patients often misreport their HBPM values, which may affect treatment decisions made by physicians on such measurements.31 Furthermore, some patients may make self-adjustment of drug treatment.10 In some cases self-measured HBPM may not be possible because of cognitive impairment or physical limitations, or may be contra-indicated because of anxiety or obsessive patient behavior, in which case ABPM may be more suitable.2

With a growing global burden of hypertension and a growing availability of affordable and accurate BP measuring devices, HBPM could be used to diagnose high BP and help decide whom to treat.32 Furthermore, with smartphone applications that accept automated data uploads from HBPM devices and display BP trends over time, HBPM could be an excellent tool to follow-up treatment and BP control, and help save time for the physicians as they conduct remote consultations exploiting electronic tools for communication.32 When an unbiased assessment of BP is obtained according to the current ESH/ESC and international guidelines, HBPM can have a primary role in the diagnosis, treatment, and long-term follow-up of the majority of our hypertensive patients, especially given the fact that they can be really cost-effective.33

References
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2. Mancia G, Fagard R, Narkiewicz K, et al. 2013 ESH/ESC guidelines for the management of arterial hypertension: the Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC). Eur Heart J. Jul 2013;34(28):2159-2219.
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Competing interests: No competing interests

16 February 2015
George Michas
Cardiology Fellow
Athens, Greece