The involvement of a health professional in the measurement of BP can affect the accuracy and reliability of the readings [13]. The failure to follow guidelines for BP measurement, as noted above, tends to provoke a white coat effect , especially in patients who may already be anxious about seeing a physician. Stimuli such as conversation can cause substantial increases in BP, potentially leading to a misdiagnosis of “white coat hypertension” [14]. On average, manual office BP in routine clinical practice is about 10/7 mmHg higher than manual BP recorded in a research study according to guidelines (Table 1.2). It is estimated that 15–25 % of patients diagnosed with mild–moderate hypertension will be normal when BP is recorded outside of the office setting such as with 24-h ambulatory BP monitoring (ABPM) or home BP [15, 16]. The presence of a white coat effect in patients already receiving drug therapy may also lead to additional, unnecessary medication, a condition called pseudo-resistant hypertension [17]. Longitudinal, clinical outcome studies have consistently reported that manual BP, even when recorded according to guidelines in a research setting, correlates poorly with target organ damage. Much stronger correlations have been seen with ABPM and home BP [18, 19].

Concerns about the accuracy of manual office BP in diagnosing hypertension have resulted in recent guidelines recommending against the use of manual BP measurement in the office for the diagnosis and management of hypertension [2, 3]. One option has been to rely upon 24-h ABPM for diagnosing hypertension and home BP for management of hypertension after therapy has been started. However, many physicians have been reluctant to abandon office BP and have chosen to use semi-automated, electronic devices as a replacement for mercury and aneroid sphygmomanometers.

Most semi-automated devices are modifications of oscillometric home BP recorders, which have been adapted for use in the office setting. The use of semi-automated recorders in major studies [20], such as the Omron-HEM 705 in the Anglo-Scandinavian Outcomes Trial (ASCOT), has prompted both primary care physicians and hypertension specialists to switch from manual BP recorders to semi-automated devices which have been validated for accuracy. Typically, the doctor or nurse follows procedures used previously with manual BP except that readings are taken without auscultation and manual cuff inflation/deflation, which reduces measurement error and observer bias. Some semi-automated recorders take two or three readings at pre-specified intervals after the start button is pressed.

Three studies [21–23] have compared the mean awake ambulatory BP or home BP with office BP readings taken with a semi-automated recorder with the patient alone in an examining room (Table 1.3). With the office BP readings being taken 2, 3, or 5 times, the mean value exceeded the out-of-office BP by 12/5, 7/4, and 4/5 mmHg, respectively. In a fourth study [24], three semi-automated BP readings taken in a hypertension clinic in the presence of a nurse or doctor were compared to home BP readings recorded using the same device by the patient. Once again, the mean semi-automated office BP was higher (9/5 mmHg) than the mean home BP. Thus, replacement of manual BP recorders with semi-automated, oscillometric sphygmomanometers does not eliminate the white coat effect , even if readings are taken with the patient resting quietly alone. Nonetheless, semi-automated devices have been quite popular in that they are readily available and relatively inexpensive. To date, there have been no studies comparing conventional manual BP with semi-automated BP in routine clinical practice, which makes it difficult to document the specific advantages the semi-automated method is presumed to have.

The most recent guidelines focus primarily on semi-automated electronic devices as the sphygmomanometer of choice for office BP readings. The ESH/ESC 2013 recommendations [2] did go one step further and recommended (fully) automated recorders capable of taking multiple BP readings with the patient resting alone. This type of BP measurement has been called “automated office BP (AOBP). ” Canadian guidelines now recommend AOBP readings in routine clinical practice [25].

The importance of AOBP in clinical practice first became evident in 2005 when Beckett and Godwin reported on AOBP readings recorded in 481 treated hypertensive patients recruited from primary care practices in the community [26]. In this population, mean AOBP (140/80 mmHg) was significantly lower than the mean of the last three routine manual BP readings (151/83 mmHg) recorded by the patients’ own family physicians. These findings were subsequently confirmed in a series of 309 patients referred for 24-h ABPM who had a mean AOBP of 132/75 mmHg compared to the last routine manual office BP of 152/87 mmHg recorded by the patient’s own family physician [27].

The main advantage of AOBP over semi-automated electronic devices is that AOBP does not require any active involvement of the patient or a health professional. The presence of a doctor or nurse when BP is measured increases the BP reading in some patients, presumably by adding to the anxiety generated by the visit itself. Having the patient take their own readings using a semi-automated device circumvents this factor, but the readings are still, on average, higher. One study [22] compared five AOBP readings taken with the fully automated BpTRU device with five readings taken by the patient while resting alone using a semi-automated sphygmomanometer. The latter BP was 5/4 mmHg higher than the AOBP, which was similar to the mean awake ambulatory BP.

As noted in the European and Canadian guidelines [2, 3, 25], an AOBP measurement has three basic components; the use of a fully automated sphygmomanometer which is capable of taking multiple readings with the patient resting quietly alone. There are currently three validated devices specifically designed for AOBP: the BpTRU [28], the Omron HEM-907 [29], and the Microlife WatchBP Office [30]. To date, most of the research into AOBP has been conducted using the BpTRU. Each of these devices is capable of taking 3–5 readings at 1 min intervals with no more than a one minute period required before the first reading is taken. The BpTRU takes five readings timed from the start of the first reading to the start of the second, whereas the other two devices record BP with a full minute from the end of one reading to the start of the next. Thus, an average AOBP reading can be taken over 5–6 min. Initially, there was some concern about the time required to take multiple AOBP readings in a busy clinical practice. However, if guidelines for recording a proper (manual or semi-automated) office BP are followed, the patient should remain quiet for 5 min before the first of at least two readings are taken. Thus, AOBP would only take longer if the doctor or nurse does not adhere to the current guidelines for office BP measurement which is likely often the case.

Studies [31, 32] using manual BP measurement have reported that as little as 10 s between readings may be all the time required to obtain an accurate measurement. Experiments conducted with the BpTRU and Omron HEM-907 have shown that readings taken at 1-minute intervals are comparable to readings taken at 2-min intervals [33]. Earlier studies using the BpTRU recorded BP at 2-min intervals, but 1 min is now recommended for an AOBP measurement [34]. Also, in most studies on AOBP, the patient was kept seated alone in a quiet room. However, AOBP values are also similar when readings are taken with the patient resting quietly in an office waiting room versus an examining room (35,36). Conventional manual BP is affected by the surroundings in which readings are taken. Such is not the case with AOBP. Readings taken with the BpTRU with the subjects resting quietly in a community pharmacy were similar to AOBP recorded in the office of their family physician [37]. Moreover, AOBP obtained in a hypertension specialist’s office was similar to AOBP taken in an ABPM unit [38]. Thus, a valid AOBP reading should be possible provided the patient is resting alone without talking or otherwise interacting with other people, especially health professionals.

Finally, the higher cost of AOBP recorders has been an impediment to their greater use in clinical practice. Recently, less expensive models have appeared which should make financial considerations much less of an issue when it comes to selecting the optimum sphygmomanometer for office use.