The current study found a great discrepancy between BP measuring methods recommended by international guidelines and those used in routine clinical practice by general practitioners in HK. Majority of general practitioners used manual office BP-measuring methods, particularly using mercury or aneroid devices, for routine screening (63.1%), diagnosis (56.4%), and management (72.4%) of HT. Furthermore, while using office BP, many doctors (26.7%) reportedly obtained only one BP reading for diagnosis and/or treatment. Similarly, 60% doctors took < 12 HBPM readings for diagnosis or management of HT. On the other hand, ABPM was prominently underutilised, with only ~ 1% of doctors using this method to diagnose HT. The other out-of-office BP measurement method, HBPM, was used by less than one-fifth of doctors for diagnosis (22.2%), though around half of the respondents (56.8%) used HBPM to guide management of HT.
Despite manual office BP measurement being most commonly used by our respondents, it is the least accurate of all methods and therefore is least able to predict cardiovascular events, as it is prone to assessment errors due to factors such as inadequate rest period prior to BP measurement, carrying on a conversation during BP measurement, obtaining inadequate numbers of BP readings, rounding-errors when recording BP value, and too rapid manual deflation of the BP cuff (21).
The over-dependence on manual office BP and the underutilisation of out-of-office BP measurements means that a substantial proportion of patients are over-treated or undertreated if they have white-coat hypertension or masked hypertension, respectively (4). Researchers have shown that ≤ 30% patients could receive unnecessary treatment, if hypertension is solely diagnosed based on office BP values, as they could simply have white-coat hypertension (4). A few studies have suggested the underlying reasons behind this preference for BP measurement methods. An Australian primary care study found that general practitioners were uncertain about the best way to measure BP, were unsure about the cut-off values for out-of-office BP estimation, did not have enough time to discuss techniques or results of ABPM or HBPM with the patients, and did not have the resources to prescribe or provide HBPM/ABPM (22); these general practitioners suggested that a dedicated primary care guideline was needed (22). Moreover, patients may not perceive the benefits of HBPM and can perceive self-monitoring of BP as inaccurate (23). Similarly, doctors are often concerned about whether the patient could master HBPM techniques and follow the strict measurement protocols required, to obtain accurate readings (24). ABPM may also be perceived by doctors as inaccessible, expensive, inaccurate, and poorly tolerated (24). Similar research in Chinese and Asian populations, especially in Hong Kong, is lacking. Although, several studies have described possible barriers to using out-of-office BP measurement methods, more studies are needed to understand how to implement accurate BP assessment techniques (e.g. ABPM/AOBP) in primary care. The current study also found that family medicine specialists were more likely to use AOBP in clinics and also to obtain enough office BP readings for diagnosis and management of HT, suggesting that targeted medical education can modify BP-measurement behaviour.
Only a few similar studies exist in the available literature. An online survey, which was conducted by the College of Family Physician of Canada and involved 774 family physicians (response rate, 16.2%), found that AOBP was a common method to screen (42.9%), diagnose (31.1%), and manage (59.2%) HT, while ABPM was reported as the primary diagnostic tool for HT by 14.4% of the respondents (17). A questionnaire-based study conducted in 2002, in Brazil, found that out of 3621 (response rate, 14.1%) physicians, 82.4% doctors routinely measured BP using either a manual aneroid or mercury device, but 86.9% routinely measured BP ≥ 1-time in a single clinic visit (18). A survey involving participants attending educational seminars on hypertension in Japan in 2010, found that out of 2995 participants, 29% used an automated device to measure BP in office settings while 68.1% used a mercury device, and 43% measured office BP only once during each visit. Direct comparison of our findings with those of these studies is difficult because, newer evidence emphasising the role of ABPM and AOBP has increasingly emerged only in the last decade. Considering the findings of the Canadian study (17), significantly fewer doctors in HK used AOBP and ABPM for diagnosis and management of HT. The reasons for this cannot be delineated from the current study, and relevant studies on the topic are lacking in the Asian/Chinese population. However, we hypothesised that this may be due to a lack of relevant guidelines in HK. Although, the HK primary care guidelines have discussed the technique of HBPM at length, both ABPM and AOBP are not mentioned (25). Secondly, most of our study-participants were old and worked in the private sector. These doctors may have used the manual technique over many years and considered it a way to build rapport with patients and demonstrate their expertise (26). Furthermore, patients may be used to, and will expect manual BP measurements, due to its widespread local use (26). Finally, doctors in the private sector are able to conduct patient-consultation for longer periods and can afford to spend time taking systematic manual measurements. These factors may at least partially explain the significant underutilisation of ABPM and AOBP in primary care in HK. A detailed qualitative study in HK, is needed to further ascertain our results and hypotheses.
Despite this being one of the first few studies to describe doctors’ preferences with respect to BP measurement methods, the study has certain limitations. Although, our response rate was low at 25.6%, this is comparable to, or even higher than those observed in previous similar surveys and e-mail studies involving doctors (17,18). Secondly, our results might have overestimated the number of doctors who used AOBP or out-of-office BP measurements because (i) the respondents were more likely to be interested and knowledgeable in BP measurements than non-respondents; and (ii) to ensure social desirability, respondents might have answered the questionnaire according to the international guidelines rather than describing techniques used in their actual clinical practices. However, these factors make our conclusion of underutilisation of out-of-office BP and AOBP measurements, even more robust. Thirdly, most of our respondents worked in the private sector and the applicability of our results to the doctors working in the public sector is unknown. Doctors working in the public sector might not have responded to the questionnaire because, they often do not have the freedom to choose a particular BP measurement method, which is determined by their respective departmental authority. Although, BP measurement practices in the public sector are not reflected by our data, reportedly, ABPM is not widely available in the public outpatient clinics, doctors working in these clinics often obtain blood pressure readings using automatic oscillatory machines (not AOBP), and recommended measurement methods (AOBP, HBPM, ABPM) are underutilised due to shorter consultation time-intervals (often only 2–5 minutes/patient) (27). On the contrary, doctors working in the private sector can choose from a range of available BP measurement methods, have the time to counsel patients, and in turn, their patients might be more willing to bear the expense and effort required for ABPM/HBPM.