The clinical value of automated office blood pressure: What is the latest evidence on attended vs unattended automated readings in clinical practice?

Cardiovascular disease (CVD) is the leading cause of death worldwide, and hypertension is the strongest risk factor for CVD and death. Inadequate blood pressure (BP) control has remained a growing problem despite antihypertensive drugs being one of the most frequently prescribed medications globally. Although meta-analyses and systematic reviews1, 2 indicated that aggressive reduction of BP reduces the risk of CVD, only a small number of randomized controlled trials on treatment targets has been published concerning the extent to which BP should be reduced. The SPRINT (Systolic Blood Pressure Intervention Trial) addressed this topic and showed that in high-risk patients intensive treatment was more beneficial in reducing cardiovascular risk and death compared to less intensive treatment.3 Although the findings of SPRINT have been clarified and treatment targets of lower blood pressure levels have been adopted in the Canadian,4 the Australian5 and more recently in the 2017 ACC/AHA Hypertension Guidelines,6 others have been reluctant to follow suit, mainly because of the escalating debate concerning the BP measurement technique in SPRINT. In that study, BP monitors were programed to allow a 5-minute rest before the first BP measurement, take three readings at 1-minute intervals, and display the average. All measurements were obtained using the OMRON HEM-907 XL device, and the method had been known as Automated Office Blood Pressure, or AOBP measurement, during the last decade. As originally described, during the AOBP measurements the patient is alone in the examination room. After the SPRINT trial, this approach has been dubbed “unattended” AOBP measurement by some authors. Although the method for measuring BP in SPRINT was intended to obtain the true baseline BP of the patient, unaffected by external factors such as white coat effect or observer influences, the actual procedures employed in the study were strongly criticized by some seasoned authors in Europe. The criticism on unattended AOBP is focused on two points: first, in a significant number of centers, a nurse remained in the examination room; and second, the original SPRINT publication did not describe in detail the exact procedure followed for the measurement of BP. In point of fact, as presented in an article by Johnson et al in Hypertension, the participants were left alone only during the rest period in 1746 cases, whereas in 570 cases remained alone only during the BP readings. Furthermore, in 2247 cases a healthcare professional remained in the room throughout both the rest period and the entire BP measurement, in contrast to 4082 participants who were always alone.7 This heterogeneity in methodology created concerns regarding the internal validity of the results. It also created new terminology, with AOBP measurements now called “attended” or “unattended.” In the SPRINT trial, attended and unattended measurements were taken from different subjects, so the values are not comparable. Still, a subsequent report claimed that the comparison between average systolic and diastolic BP measurements between the two modalities essentially revealed no difference. Filipovský et al compared unattended AOBP with manual office and home in the same subjects. Their study, performed in a specialized hypertension center, found unattended systolic office BP not only to be lower than conventional manual office BP readings but also 6 mm Hg lower than home BP.8 Similarly, Papademetriou et al investigated the correlation of unattended SPRINT-like measurements with other conventional BP measurements and concluded that all BP measurements were similar with no statistically significant difference.9 On the other hand, a cross-sectional study of 158 patients conducted in the offices of four general practitioners compared conventional auscultatory office BP and unattended AOBP measurements in 107 subjects, and unattended and attended AOBP in another 51 subjects.10 Attended and unattended office BP failed to show a significant difference in either group, suggesting that unattended and attended office measurements achieved comparable values. In the wake of the SPRINT study and the controversy it generated, we performed a study comparing head-to-head BP readings with the nurse present (albeit with no interaction taking place), or absent, in order to compare attended and unattended AOBP. Our findings showed very similar results between the two measurements. These readings were taken either before or after conventional office measurements, and these values were compared against conventional office and daytime ambulatory BP readings.11 AOBP readings had similar values when BP measurements were taken in the presence or absence of medical staff (mean systolic attended AOBP was higher by 0.6 mm Hg on average), suggesting similar values of this technique when the patient rests for 5 minutes in a quiet examining room. AOBP, attended and unattended, taken either before or after the office readings, also had a small mean difference (mean systolic unattended AOBP was higher by 1.4 mm Hg on average). SPRINT findings, in which BP measurements were taken with or without staff present, are largely comparable with the results of our study which determines variation in BP measurement techniques. Similarly, no differences were observed among BP values independently of whether BP measurements were performed in the presence or absence of healthcare professionals. We believe that the novelty of the SPRINT in BP measurement is that allowing a 5-minute rest before performing three BP readings can prevent falsely elevated BP values, a common finding in routine clinical practice. The findings of Andreadis et al11 are timely and of significant clinical value because they provide insight into the great SPRINT debate regarding the protocol for BP measurements followed by the researchers and suggest AOBP is the technique of choice in the office setting. The 5-minute rest period is now considered essential in clinical practice and is described in the 2017 ACC/AHA Hypertension Guidelines as a common error that can lead to inaccurate estimation of BP if not implemented. There is concern that the prescribed rest period before BP recording may not be compatible with daily clinical practice in most offices. As an alternative, AOBP readings taken with the BpTRU equipment use five readings at 1-minute intervals and do not require the preceding 5 minutes of rest. They provide similar values to the mean awake ambulatory BP, and both techniques measure values that are significantly lower than the manual BP readings. It is essential to attenuate the white coat effect in BP measurements. There is growing evidence supporting the merits of AOBP in this regard. This technique, either in its latest attended version (but strictly without conversation between patient and examiner) or in the original unattended one, could be adopted as the optimal method for BP measurement in the clinical setting. The authors report no conflict of interest.

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