The COVID-19 pandemic, coupled with an updated recommendation from the US Preventive Services Task Force (USPSTF) and recent policy statement from the American Heart Association/American Medical Association (AHA/AMA), clearly document the need and value of self-measured blood pressure monitoring (SMBP).
On June 23, 2020, in a draft update of its hypertension screening guidelines for clinicians, the USPSTF gave a Grade A recommendation to “screening for hypertension in adults age 18 years or older with office blood pressure measurement (OBPM)” and “obtaining blood pressure measurements outside of the clinical setting for diagnostic confirmation before starting treatment.” A “Grade A” recommendation is the highest level given by USPSTF and indicates that there is high certainty that the net benefit of the recommendation is substantial.
Hypertension is one of the most important risk factors for cardiovascular disease, the leading cause of death in the United States. Hypertension is also a risk factor for chronic kidney disease. Almost half of Americans 20 years of age or older have hypertension (high blood pressure) which since 2017 has been defined as a systolic blood pressure ≥130 mm Hg or a diastolic blood pressure ≥80 mm Hg or use of medication to control blood pressure. Since most patients with hypertension have no symptoms of the condition, screening is necessary to detect it.
Traditionally, blood pressure screening has been done in a clinician’s office, however published research suggest that many factors contribute to inaccurate measurements in this setting. Patient related factors include acute meal ingestion; acute alcohol, caffeine, or nicotine use; bladder distention; cold exposure; or insufficient rest. Another patient related factor is the “white-coat effect”, presumably due to anxiety related to having a blood pressure measurement in the clinician office. Device related factors include the use of inaccurate or uncalibrated instruments. Procedure related factors include improper positioning of the patient, incorrect cuff size, insufficient time between repeat measurements, and talking with the patient during measurement. For clinical settings that use non-automated devices, procedure related factors can also include improper cuff inflation or deflation rates and observer errors due to hearing impairment or terminal-digit preference bias (the tendency to choose “0” rather than another digit, e.g., 120/80 rather than 118/82).
To avoid all these factors in a busy clinical setting indeed may be near impossible and has led to the USPSTF recommendation for “obtaining blood pressure measurements outside of the clinical setting for diagnostic confirmation before starting treatment.” A natural extension of this recommendation is that outside blood pressure measurements should also be employed during the management of patients with hypertension. Indeed, Michael Rakotz, MD, an author of the AHA/AMA policy statement stated in a recent interview: “Self-Measured Blood Pressure Monitoring (SMBP) is the most practical way to obtain out-of-office BP measurements and can be used to assess the effectiveness of treatment for patients who have hypertension.” Noting increasing evidence of the association of between SMBP measure and relevant clinical outcomes he also said: “Compared with routine blood pressure measurements obtained in an office setting, SMBP measurements are a better predictor of cardiovascular disease and premature death.”
SMBP can also be used to identify white-coat and masked hypertension and can be used to monitor the progression of whitecoat to sustained hypertension. White-coat hypertension is defined as having high office BP measurements with normal BP outside the office. Masked hypertension is defined as having normal office BP measurements and high out of the office measurements. White-coat hypertension is associated with no increase or moderately increased risk of cardiovascular disease whereas masked hypertension is associated with elevated risk of cardiovascular disease. Four U.S. and ten international guidelines recommend the use of SMBP for the indications discussed above as well as assessment of BP control during treatment, assessing long-term BP control, and motivating treatment adherence.
Translating these recommendations into personally actionable guidance is challenging. Coupling these recommendations with my many years of clinical practice and quality improvement research in primary care practice, I suggest the following groups of people, 18 years of age or older, consider SMBP:
- Those who do not have a regular source of primary health care: Due to general good health, geographic location, financial barriers or other reasons, many people do have a primary care clinician.
- Those who are healthy and do not want to visit their primary care clinician due to cost, inconvenience, or concerns about the current COVID-19 pandemic.
- Those with a regular source of primary care who are concerned that their blood pressure is not accurately obtained in their clinician’s office due to one or more of the factors discussed above.
- Those with elevated BP (systolic between 120 and 130, diastolic <80) to monitor for the development of hypertension (BP > 130/80).
- Those who have just received a diagnosis of hypertension in a clinician’s office to confirm the diagnosis by assessing whether they have “white coat” hypertension.
- Those whose BP is normal in their clinician’s office but suspect that they may have hypertension, that is “masked hypertension.”
- Those with hypertension who want to monitor their treatment more accurately than possible with clinician office visits.
In the aggregate these groups represent nearly half of the adult American population and likely similar proportions in much of the rest of the world.