How in-office and ambulatory BP monitoring compare: A systematic review and meta-analysis

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Original Research

How in-office and ambulatory BP monitoring compare: A systematic review and meta-analysis

J Fam Pract. 2017 January;66(1):E5-E12

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References

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DISCUSSION

The European Society of Hypertension still regards office BP measurement as the gold standard in screening for, diagnosing, and managing hypertension. As previously mentioned, though, office measurements are usually handled by medical staff and can be compromised by the white-coat effect and a small number of measurements. The USPSTF now considers ABPM the reference standard in primary care to diagnose hypertension in adults, to corroborate or contradict office-based determinations of elevated BP (whether based on single or repeated-interval measurements), and to avoid overtreatment of individuals displaying elevated office BP yet proven normotensive by ABPM.^4,7 The recommendation of the American Academy of Family Physicians is similar to that of the USPSTF.⁷ Therefore, evidence supports ABPM as the reference standard for confirming elevated office BP screening results to avoid misdiagnosis and overtreatment of individuals with isolated clinic hypertension.⁷

How office measurements stack up against ABPM

Checking the validity of decisions in clinical practice is extremely important for patient management. One of the tools used for decision-making is an estimate of the LR. We used the LR to assess the value of office BP measurement in determining controlled or uncontrolled BP. A high LR (eg, >10) indicates that the office BP can be used to rule in the disease (uncontrolled BP) with a high probability, while a low LR (eg, <0.1) could rule it out. An LR of around one indicates that the office BP measurement cannot rule the diagnosis of uncontrolled BP in or out.²⁷ In our meta-analysis, the positive LR is 1.35 and negative LR is 0.44. Therefore, in treated hypertensive patients, an indication of uncontrolled BP as measured in the clinic does not confirm a diagnosis of uncontrolled BP (as judged by the reference standard of ABPM). On the other hand, the negative LR means that normal office BP does not rule out uncontrolled BP, which may be detected with ABPM. Consequently, the measurement of BP in the office does not change the degree of (un)certainty of adequate control of BP. This knowledge is important, to avoid overtreatment of white coat hypertension and undertreatment of masked cases.

As previously mentioned, we reported similar results in a study designed to determine the validity of office BP measurement in a primary care setting compared with ABPM.¹³ In that paper, the level of agreement between both methods was poor, indicating that clinic measurements could not be recommended as a single method of BP control in hypertensive patients.

The use of ABPM in diagnosing hypertension is likely to increase as a consequence of some guideline updates.²Our study emphasizes the importance of their use in the control of hypertensive patients.

Another published meta-analysis¹ investigated the validity of office BP for the diagnosis of hypertension in untreated patients, with diagnostic thresholds for arterial hypertension set at 140/90 mm Hg for office measurement, and 135/85 mm Hg for ABPM. In that paper, the sensitivity of office BP was 74.6% (95% CI, 60.7-84.8) and the specificity was 74.6% (95% CI, 47.9-90.4).

In our present study carried out with hypertensive patients receiving treatment, we obtained a slightly higher sensitivity value of 81.9% (within the CI of this meta-analysis) and a lower specificity of 41.1%. Therefore, the discordance between office BP and ABPM seems to be similar for the diagnosis of hypertension and the classification of hypertension as being well or poorly controlled. This confirms the low validity of the office BP, both for diagnosis and monitoring of hypertensive patients.

Strengths of our study. The study focused on (treated) hypertensive patients in a primary care setting, where hypertension is most often managed. It confirms that ABPM is indispensable to a good clinical practice.

Limitations of our study are those inherent to meta-analyses. The main weakness of our study is the paucity of data available regarding the utility of ABPM for monitoring BP control with treatment in a primary care setting. Other limitations are the variability in BP thresholds used, the number of measurements performed, and the ambulatory BP devices used. These differences could contribute to the observed heterogeneity.

Application of our results must take into account that we included only those studies performed in a primary care setting with treated hypertensive patients.

See the related PURL on ambulatory BP monitoring at http://bit.ly/2i24hoi.

Moreover, this study was not designed to evaluate the consequences of over- and undertreatment of blood pressure, nor to address the accuracy of automated blood pressure machines or newer health and fitness devices.

Implications for practice, policy, or future research. Alternative monitoring methods are home BP self-measurement and automated 30-minute clinic BP measurement.²⁸ However, ABPM provides us with unique information about the BP pattern (dipping or non-dipping), BP variability, and mean nighttime BP. This paper establishes that the measurement of BP in the office is not an accurate method to monitor BP control. ABPM should be incorporated in usual clinical practice in primary care. Although the consequences of ambulatory monitoring are not the focus of this study, we acknowledge that the decision to incorporate ABPM in clinical practice depends on the availability of ambulatory devices, proper training of health care workers, and a cost-effectiveness analysis of its use.

CORRESPONDENCE
Sergio Reino-González, MD, PhD, Adormideras Primary Health Center, Poligono de Adormideras s/n. 15002 A Coruña, Spain; sergio.nelson.reino.gonzalez@sergas.es.