Response to Measurement of Blood Pressure in the Office
The letter by Martin et al1 raises several interesting issues related to the office measurement of blood pressure (BP). As discussed in our article,2 the conditions under which manual BP readings are measured and characteristics of the patient population need to be taken into account when interpreting the results. Readings recorded as part of a research study are often not comparable to BP obtained in routine clinical practice. Thus, an algorithm derived from “research-quality” BP may not be appropriate for interpreting readings taken during routine clinical encounters.3 The algorithm that we proposed has been tested against routine BP readings taken by the patients’ own family physicians. In 254 untreated patients, automated office (AO) BP was much better at determining BP status using the mean awake ambulatory BP as a gold standard.4
It is difficult to interpret the BP data provided by Martin et al1 without knowing more about the patient population and how the measurements were obtained. What is clear is that these readings were taken as part of a research study. More attention needs to be paid to the circumstances under which BP is measured. All BP readings may be affected by the degree to which measurement techniques adhere to guidelines. What is clear is that manual BP is affected much more by the quality of the reading than is AOBP. We have recommended that the gap between research and clinical practice in terms of how BP is measured be explicitly acknowledged and have proposed a pragmatic solution to bridge it.2
We agree with Martin et al1 that patients with borderline BP based on AOBP readings should be assessed by 24-hour ambulatory BP monitoring (ABPM), if available, or home BP as shown in the algorithm. If ABPM is normal, continued follow-up with AOBP would seem to be indicated, with further evaluation of out-of-office BP being performed if AOBP readings increase. If ABPM (when available) or home BP is high, then drug therapy should be considered. However, for those patients who remain in the borderline range, and there will always be some, follow-up with AOBP and/or home BP is indicated. Because ABPM is not universally available and is relatively expensive, it would seem more practical to monitor patients with AOBP and home BP, limiting repeat ABPM recordings for those individuals who exhibit a change in BP status. Further research into the relationship among AOBP, home BP, and ABPM should provide more guidance on how to interpret AOBP readings under different conditions or when applied to different populations.
Martin CA, Cameron JD, Chen SS, McGrath BP. Measurement of blood pressure in the office. Hypertension. 2010; 56: e11.
Myers MG, Godwin M, Dawes M, Kiss A, Tobe SW, Kaczorowski J. Measurement of blood pressure in the office: recognizing the problem and proposing the solution. Hypertension. 2010; 55: 195–200.
Myers MG. Response to comparing blood pressure measurement methods: differences depend on blood pressure height. Hypertension. 2010; 56: e5.