Home blood pressure monitoring may make office measurements obsolete

Abstract

The conventional measurement of blood pressure (BP) in the office or clinic has been the cornerstone for hypertension management for decades. However, because of the white-coat and the masked hypertension phenomena, out-of-office BP monitoring with ambulatory or home measurements is often required [1]. Extensive research on ambulatory BP monitoring has established its role as the most accurate tool for hypertension diagnosis [1–3]. On the contrary, despite the increasing use of home BP monitoring by hypertensive patients in the daily management of their high BP condition, research in this field, in particular when considering outcome trials, has been delayed as compared to ambulatory BP monitoring [4,5]. PROGNOSTIC ABILITY OF HOME BLOOD PRESSURE The ultimate criterion to identify a useful method for the assessment of a cardiovascular risk factor in clinical practice is its actual ability to predict future cardiovascular events. This holds true also when considering the different methods now available for BP measurement. In this issue of the journal Ward et al.[6] summarize the available evidence on the prognostic value of self-BP measurements performed by patients at home, through a systematic review and meta-analysis of outcome trials using home BP monitoring. The strength of this analysis is that it includes data from eight prospective studies and 17 688 patients followed for 3.2–10.9 years, which results in the availability of information based on almost 100 000 person-years of follow-up [6]. When focusing on the results of this meta-analysis, it has to be considered that there were important differences among these studies, mainly involving the study population (general population samples, patients registered in primary care or treated hypertensive patients), the BP measurement protocol (observer, device type, measurement number and schedule), and the primary endpoints and statistical adjustments. Despite the considerable clinical and methodological heterogeneity of these studies, a meaningful comparison of the prognostic ability of home versus office BP was possible, because in most of these studies both methods have been applied to the same participants. The meta-analysis of these studies [6] showed home BP to be superior to office measurements, with this difference being beyond chance for systolic BP (Table 1).TABLE 1: Hazard ratios for cardiovascular events per 10 mmHg increase in systolic or 5 mmHg diastolic office and home blood pressureA brief review and meta-analysis of the results of the same eight outcome studies was previously reported [7] and as expected gave almost identical hazard ratios for cardiovascular events (Table 1). The meta-analysis by Ward et al.[6] provides a valuable additional contribution, by offering results for prediction of all-cause and cardiovascular mortality, which were significant for home but not for office systolic BP. These data thus allow a major step forward in establishing the clinical usefulness of home BP monitoring in the management of hypertension in clinical practice. OFFICE AND HOME BLOOD PRESSURE MEASUREMENT, OR HOME MEASUREMENT ALONE? In 2007 Pickering et al.[8] questioned the usefulness of the conventional BP measurements taken by the doctor in the office. Given that office measurements often induce the white-coat phenomenon, it was suggested that a diagnosis of hypertension based on elevated office BP would require confirmation by out-of-office measurements. However, because of the masked hypertension phenomenon, the finding of normal or low office BP would also require confirmation by out-of-office measurement [8]. Moreover, it is recognized that in cases with disagreement between office and out-of-office measurements the risk is best predicted by out-of-office measurements [1,4,5]. The practical interpretation of these data, if examined without the influence of the long tradition with classic office measurements, led to the straightforward conclusion that, once reliable out-of-office BP measurements are available, the classic office measurements should become obsolete. The provocative proposal to abandon office BP measurement is further supported by additional and more informative analyses that consider both home and office BP measurements in the same adjusted models. This challenging research question was addressed using different analytic approaches in five outcome studies. Four of these studies [9–12] showed that when both methods were considered, home and not office BP remained a significant predictor of risk. One study showed that the two methods provided independent information, yet the potential of home BP was not exhausted because this was based on two readings only [13]. Ward et al.[6] performed a meta-analysis of three studies (n = 6013) [9–11] and showed that home BP retains its prognostic ability after adjustment for office BP. On the contrary, office BP lost its significance after adjustment for home BP [6]. It is clear from these findings that the availability of home BP measurements is likely to make office measurements obsolete. The above evidence does not imply that in our times the conventional office BP measurement has no role. This time-honoured technique remains a valuable initial massive screening test to be applied by healthcare providers at all levels. Moreover, office visits are still necessary for the follow-up of disease symptoms, adverse effects of drugs, lifestyle modification and patients’ compliance. However, doctors should realize that the assessment of the BP level on the basis of conventional office BP measurements is largely incomplete. Recently, the British National Institute for Health and Clinical Excellence (NICE) guidelines have suggested that the diagnosis and treatment decision in hypertension should no longer be based on office measurements alone, and that confirmation by out-of-office measurements should be mandatory [14]. Another issue to consider is that although it is agreed that treatment decisions in isolated office hypertension should be guided by out-of-office BP measurements, elevated office BP in these cases seems to represent an intermediate phenotype of hypertension that requires follow-up due to increased risk of future hypertension. Interestingly, in the PAMELA general population study with 12-year follow-up, office, home and ambulatory BP measurements provided a significant additive contribution to prediction of cardiovascular mortality [15], suggesting that all the three measurement methods offer complementary rather than redundant information on patients’ BP levels. HOME OR AMBULATORY BLOOD PRESSURE MEASUREMENT? When Pickering et al.[8] posed the question ‘Should doctors still measure blood pressure?’, they came to the conclusion that ‘the best established technique for out-of-office BP measurement is ambulatory monitoring, and home monitoring may also be applicable in the future’. This position was based on the fact that the fundamental research questions regarding the role of ambulatory BP had been investigated almost one decade earlier than for home BP [1–5]. In the same line, the 2011 UK NICE guidelines for the clinical management of hypertension recommended that all patients with elevated office BP should have ambulatory monitoring to confirm the diagnosis of hypertension [14]. Home BP monitoring was also proposed as a suitable alternative to confirm the diagnosis of hypertension in patients who are unable to tolerate ambulatory monitoring [14]. It is clear that the NICE approach has focused on the white-coat phenomenon, but ignored the almost equally common but more clinically relevant phenomenon of masked hypertension. Indeed the latter is more difficult to address because the population at risk (requiring screening for masked hypertension) is less clearly defined and probably larger than that with elevated office BP [12,16]. Home BP monitoring represents a diagnostic tool at least in part similar to ambulatory monitoring, because both methods provide multiple measurements away from the office in the usual environment of each individual and under routine daily conditions. However, these methods also have important differences because home measurements are taken only in the sitting posture and always at home, whereas ambulatory monitoring is performed during various routine daily conditions at home, at work and during sleep. Despite these differences, home and ambulatory BP appear to have similar advantages, in terms of reproducibility, and ability to diagnose the white-coat and masked hypertension phenomena [16] and to predict target organ damage [4,5] and cardiovascular events [6,7]. When considering their similarities and differences all together, home and ambulatory BP monitoring appear to be complementary rather than competitive methods and when used in combination provide a more complete picture of the individual's BP profile [4]. Moreover, the recent evidence on the prognostic ability of home BP [6,7] suggests that this method should no longer be regarded only as a preliminary screening test requiring confirmation by ambulatory monitoring, but as a reliable diagnostic test, alternative to ambulatory monitoring, to be used for decision-making in hypertension management. Home BP should be suitably combined with ambulatory monitoring, however, when information on 24-h BP variability, circadian profile and night-time BP is regarded as important. Equipment availability, cost of use and patients’ preference are important factors that should influence the decision on which method to prefer each time, yet all these factors favour the routine use of home monitoring [4,5]. In general, ambulatory monitoring appears to be more suitable for the initial diagnostic assessment of elevated BP and for the evaluation of treatment effects on 24-h BP variability, whereas home monitoring is more suitable for the long-term follow-up of treated hypertension. HOME BLOOD PRESSURE MONITORING FOR ALL PATIENTS WITH HYPERTENSION OR HIGH-NORMAL BLOOD PRESSURE As mentioned in the 2011 NICE guidelines, it is likely that there will be an increasing use of home and ambulatory BP monitoring for the diagnosis of hypertension as a consequence of the guidelines update [14]. Recent European and American guidelines have also endorsed the application of home BP monitoring in the management of hypertension in clinical practice and recommended its use in most patients with possible or treated hypertension [4,5]. Patients with elevated or borderline office BP levels, those with initially elevated office BP which normalizes with repeated measurement, patients at high total cardiovascular risk, as well as all treated hypertensive patients are likely to greatly benefit from home BP monitoring [4,5,12,16,17]. In a landmark position study in 2008 Pickering et al.[5] called for action aiming at a wider use and also at reimbursement of home BP monitoring in clinical practice, similarly to what is already done with devices for self-monitoring of blood glucose, which are reimbursed in patients with diabetes. While waiting for this sensible proposal to be approved by healthcare systems, a step which might be delayed due to current global financial constraints, it should be realized that in many countries patients with hypertension have made the decision to cover the cost of the technique themselves. Given that the method is readily available and its wide use is now also supported by strong evidence on its prognostic relevance [6,7] and recommended by international and national hypertension societies, it is time for physicians to take control of this increasingly popular approach to hypertension management, by supervising the technique according to current guidelines, aiming at better BP control, increased patients’ compliance with prescribed treatment and improved prognosis [4,5]. ACKNOWLEDGEMENTS Conflicts of interest There are no conflicts interest.