Attended automated office blood pressure re‐visited

Guidelines for the measurement of blood pressure (BP) were first published by the American Heart Association in 1939.1 During the subsequent decades, there were few changes, with the mercury sphygmomanometer continuing to be the standard technique for recording blood pressure in the office setting. Only recently has there been a transition to automated devices using oscillometric technology, culminating in automated office (AO) BP, which involves a fully automated sphygmomanometer capable of taking multiple BP readings with the patient resting alone in a quiet place. The main advantage of AOBP is that it virtually eliminates the white coat effect associated with routine office BP readings, with mean AOBP being similar to the mean awake ambulatory (A)BP,2 a gold standard for future cardiovascular risk related to BP status. Scientific committees of both Hypertension Canada3 and the American Heart Association4 have carefully evaluated the use of AOBP in clinical practice, concluding that it should be the preferred technique. Any consideration of office BP measurement must also take into account the setting in which the readings are taken. BP recorded in routine clinical practice is not the same as readings recorded in research studies, with the latter usually adhering more closely to standard BP measurement guidelines. In a recent meta-analysis,2 routine office systolic BP in 9 studies was 14.5 mm Hg higher than mean AOBP, whereas in 9 research studies office systolic BP was only 7.0 mm Hg higher. Most of these comparisons involved manual office BP recorded with a stethoscope and mercury sphygmomanometer. However, even when duplicate office BP readings were obtained using an oscillometric device in 27 211 hypertensive subjects in primary care, the mean systolic reading was 25 mm Hg higher than the awake ABP.5 Thus, simply replacing the mercury sphygmomanometer with an automated, oscillometric device does not necessarily improve the accuracy of readings, since they may still be subject to a marked white coat effect as manifested by a higher systolic BP. The key to the success of AOBP has been the virtual elimination of the human element, such that conversation with the patient is no longer possible and anxiety provoked by the presence of office staff is eliminated. The enhanced accuracy of AOBP compared to conventional office readings has not been much of an issue. Instead, hypertension experts critical of AOBP have focused on its feasibility, expressing concerns that it takes more time to perform the measurements and that they require a separate room (or at least a quiet place in the office). The cost of devices for recording AOBP has also been mentioned. In reality, AOBP only takes longer if compared to a single office BP reading obtained without 5 minutes of antecedent rest. Also, when the AOBP is being recorded, the office staff can be performing other tasks, whereas, if present during the reading, they are often engaged in conversation with the patient which increases BP.6 It is true that AOBP should be obtained in a quiet place. Ideally, the setting should be a separate room, but having the patient seated alone in an office waiting room may also be sufficient.7 The absence of a suitable place for AOBP is not a valid reason for continuing to diagnose and treat hypertension on the basis of inaccurate office BP readings. Similarly, the cost of purchasing new AOBP recording devices should be irrelevant when it comes to the optimum care of patients. Some experts, primarily in Europe, have questioned the need to have the patient alone when performing AOBP measurements.8 Instead, they have proposed that office staff can remain present when attended AOBP readings are taken, provided that no conversation takes place. A meta-analysis9 of 5 research studies which were specifically designed to compare attended and unattended AOBP found that the mean attended systolic AOBP was still 5.8 mm Hg higher than the unattended value, with the difference being statistically significant. Considering all we have learned about BP measurement, especially in routine clinical practice, it is difficult to understand why one would want staff to be present when BP is being recorded. In the present issue, Keeley et al10 have compared attended and unattended AOBP in patients with cardiovascular disease. With both techniques, the mean systolic AOBP was normal, being <130 mm Hg. Even though there is less white coat effect in this range of BP,2 the authors reported that the attended systolic AOBP was still 2.7 mm Hg higher than the unattended value, with the difference being statistically significant. A routine office systolic BP (130.6 mm Hg) recorded with an automated sphygmomanometer in their cardiac clinic was 5.2 and 8.0 mm Hg higher than the attended and unattended AOBP readings, respectively. However, it was not possible to determine the magnitude of any white coat effect with any of these readings, since their study did not include ambulatory BP monitoring. Although the mean difference between attended and unattended AOBP was relatively small in this mostly normotensive study population, there were still more patients with an attended systolic BP > 140 mm Hg than with unattended measurements. As the authors noted, even relatively small increases in BP in patients with cardiovascular disease may be of clinical importance. The findings of Keeley et al are consistent with other studies comparing attended vs unattended AOBP and support the recommendation that AOBP should be recorded with the patient being alone. No conflicts of interest to declare.

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