How is high blood pressure diagnosed?

According to the 2017 American College of Cardiology and American Heart Association hypertension guidelines, the diagnosis of hypertension is based on an average of two or more careful blood pressure readings on two or more occasions when the patient is relaxed, sitting for more than five minutes, and has not done anything recently to increase BP such as smoke or exercise.¹ The diagnostic threshold set by the guidelines in 2017 is ≥130/80 mm Hg. The previous threshold from the 2003 JNC7 guidelines was ≥140/90 mm Hg.^2,3

The 2017 guidelines indicate specific techniques for consistent and accurate measurement of blood pressure in the office.¹ Most protocols specify proper cuff size, patient position, and timing, frequency, and number of blood pressure readings that are recommended before blood pressure readings are considered reliable.⁴

The United States Preventive Services Task Force specifies an evidence-based protocol for measuring blood pressure using the mean of two measurements from a seated patient at least five minutes after sitting down.⁴ The cuff size should be appropriate for the patient’s arm circumference and the arm supported at heart level. Multiple measurements improve the predictive power of blood pressure over a single measurement. Ambulatory and home monitoring can be used to confirm the diagnosis.

Blood pressure variability allows the body to adapt to changes in its environment and respond optimally to circumstances.⁵ It can be temporarily increased by stress, pain, exercise, medications, caffeine, and nicotine.⁴ For some people, it is also affected by the presence of a medical professional, a phenomenon known as white-coat hypertension.⁶ High blood pressure can also be falsely low in the doctor’s office, a condition referred to as masked hypertension.⁷ Masked hypertension has been shown to be associated with increased cardiovascular risk and target organ damage.^7–9

Because there is often considerable variation between blood pressure readings obtained in the office and those taken at home, ambulatory and home monitoring devices are now recommended by several professional organizations.^1,2,4,10  The 2017 guidelines found strong evidence to support the recommendation of the use of out-of-office blood pressure measurement to confirm the diagnosis of hypertension after initial identification of high blood pressure readings in the office or clinic.¹

^References

1. Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPMACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2017; 71 (19): e127-e248.
2. Chobanian A V., Bakris GL, Black HR, et al. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003; 42 (6): 1206-1252.
3. James PA, Oparil S, Carter BL, et al. 2014 evidence-based guideline for the management of high blood pressure in adults: report from the panel members appointed to the Eighth Joint National Committee (JNC 8). JAMA 2014; 311 (5): 507-520.
4. Siu AL, Bibbins-Domingo K, Grossman D, et al. Screening for high blood pressure in adults: U.S. preventive services task force recommendation statement. Ann Intern Med 2015; 163 (10): 778-786.
5. Islam MS. Ambulatory blood pressure monitoring in the diagnosis and treatment of hypertension. Adv Exp Med Biol 2017; 956 : 109-116.
6. Cohen JB, Cohen DL. Integrating out-of-office blood pressure in the diagnosis and management of hypertension. Curr Cardiol Rep 2016; 18 (11).
7. Franklin SS, O’Brien E, Thijs L, Asayama K, Staessen JA. Masked hypertension: a phenomenon of measurement. Hypertension 2015; 65 (1): 16-20.
8. Pickering TG, Davidson K, Gerin W, Schwartz JE. Masked hypertension. Hypertens (Dallas, Tex 1979) 2002; 40 (6): 795-796.
9. Anstey DE, Pugliese D, Abdalla M, Bello NA, Givens R, Shimbo D. An update on masked hypertension. Curr Hypertens Rep 2017.
10. Parati G, Stergiou G, O’Brien E, et al. European Society of Hypertension practice guidelines for ambulatory blood pressure monitoring. J Hypertens 2014; 32 (7): 1359-1366.