From the Guidelines
Hypertension is diagnosed when a person has consistently elevated blood pressure readings, with stage 1 hypertension defined as a systolic blood pressure of 130-139 mmHg or diastolic blood pressure of 80-89 mmHg, and stage 2 hypertension defined as a systolic blood pressure of 140 mmHg or higher or diastolic blood pressure of 90 mmHg or higher, as per the 2017 American College of Cardiology/American Heart Association guideline 1. To diagnose hypertension, blood pressure should be measured at least twice during each of at least two separate office visits, with the average of these readings used to determine if hypertension is present.
- The 2017 guideline replaces the term “prehypertension” with “elevated BP” (average SBP of 120 to 129 mm Hg and average DBP <80 mm Hg) and “stage 1 hypertension” (average SBP of 130 to 139 mm Hg or average DBP of 80 to 89 mm Hg) 1.
- Stage 2 hypertension is defined as an average SBP of at least 140 mm Hg or an average DBP of at least 90 mm Hg instead of a BP of at least 160/100 mm Hg 1. Home blood pressure monitoring or ambulatory blood pressure monitoring over 24 hours may also be used to confirm the diagnosis, as some patients experience "white coat hypertension" where blood pressure is only elevated in clinical settings 1.
- The guideline recommends greater use of out-of-office BP measurements to confirm the diagnosis of hypertension and titrate medication 1. These diagnostic thresholds are important because hypertension significantly increases the risk of cardiovascular disease, stroke, kidney disease, and other health problems when left untreated, with adults with BP in the stage 1 hypertension range having an approximately 2-fold increase in CVD risk compared with adults with normal BP 1. Proper diagnosis ensures appropriate treatment can be initiated to reduce these risks.
From the Research
Diagnostic Criteria for Hypertension
The diagnosis of hypertension is based on multiple blood pressure measurements, taken on at least two separate occasions 2. The criteria for diagnosing hypertension include:
- Systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg or current antihypertensive drug therapy 2
- Systolic blood pressure ≥ 130 mmHg or diastolic blood pressure ≥ 80 mmHg based on home blood pressure monitoring 3
- Daytime blood pressure mean exceeding 135/85 mm Hg based on 24-hour ambulatory blood pressure monitoring 4
Blood Pressure Measurement
Blood pressure measurements can be taken in different positions, including:
- Seated position, which is known to have limited accuracy in detecting high blood pressure 5
- Standing position, which has been shown to outperform seated blood pressure in diagnosing hypertension 5
- Multiple measurements taken over a period of time, such as 24-hour ambulatory blood pressure monitoring or home blood pressure monitoring 4, 3
Number of Measurements Needed
The number of blood pressure measurements needed to diagnose hypertension is not well-defined, but studies suggest that:
- At least two separate occasions are needed to confirm the diagnosis of hypertension 2
- 8-10 blood pressure readings may be sufficient to give a clinically useful approximation of the daytime mean blood pressure and diagnose hypertension accurately 4
- 3 days or less of home blood pressure monitoring may be enough to identify or exclude high home blood pressure with a high degree of confidence 3
- The mean of the first two blood pressure readings may be sufficient for the diagnosis of hypertension, unless the blood pressure difference between the two readings is at least 10 mmHg for both systolic and diastolic 6