From the Guidelines
Hypertension is diagnosed when a person's blood pressure consistently measures 130/80 mmHg or higher, as defined by the 2020 International Society of Hypertension global hypertension practice guidelines 1. To properly diagnose hypertension, blood pressure should be measured on at least two separate occasions, typically a few weeks apart, using a validated blood pressure measuring device with an appropriate cuff size for the individual patient. The measurement should be taken after the person has been seated quietly for at least 5 minutes with their back supported, feet flat on the floor, and arm supported at heart level. Multiple readings should be taken during each visit, with at least 1 minute between readings, and the average calculated. Some key points to consider when diagnosing hypertension include:
- Repeated office BP ≥140/90mmHg indicates hypertension, particularly if home BP ≥135/85mmHg or 24h ambulatory BP ≥130/80mmHg 1.
- Home blood pressure monitoring is also valuable, with readings taken twice daily (morning and evening) for at least 7 days before a diagnosis.
- Ambulatory blood pressure monitoring, which measures blood pressure over 24 hours, can provide additional information and help identify white coat hypertension (elevated readings only in clinical settings) or masked hypertension (normal readings in clinical settings but elevated elsewhere). Once hypertension is diagnosed, additional tests are typically performed to assess for organ damage and identify secondary causes, including blood tests for kidney function, electrolytes, glucose, and cholesterol, as well as urinalysis, electrocardiogram, and sometimes echocardiography. Proper diagnosis is crucial because hypertension often has no symptoms but significantly increases the risk of heart disease, stroke, kidney disease, and other serious health problems if left untreated, as highlighted by the 2020 U.S. Department of Veterans Affairs/U.S. Department of Defense clinical practice guideline 1.
From the Research
Diagnosing Hypertension
To diagnose hypertension, the following steps can be taken:
- Multiple blood pressure measurements should be taken on at least two separate occasions 2
- Blood pressure should be measured on at least two office visits, both for clinical purposes and in epidemiological studies 2
- Out-of-office blood pressure measurements, including 24-hour ambulatory blood pressure monitoring (ABPM) and home blood pressure monitoring (HBPM), can be used to accurately diagnose and treat hypertension 3
- ABPM is recommended for the initial diagnosis of hypertension, assessment of BP phenotypes and circadian patterns, and detection of nocturnal hypertension 3
- HBPM is recommended for diagnosing hypertension and assessing BP phenotypes, and is preferred over ABPM for the long-term follow-up of patients with hypertension 3
Blood Pressure Measurement
- A single blood pressure measurement is not sufficient to diagnose hypertension, as blood pressure fluctuates with time 4
- About 8-10 blood pressure readings are sufficient to give a clinically useful approximation of the daytime mean blood pressure and therefore for diagnosing hypertension accurately 4
- Measuring blood pressure during the afternoon gives the best agreement with the 24h blood pressure mean 4
- Blood pressure measurements should be taken using validated automated oscillometric devices, and patients should be educated on proper blood pressure measurement techniques 3
Importance of Accurate Diagnosis
- Accurate diagnosis of hypertension is crucial to prevent misdiagnosis and mistreatment 2, 3
- Misdiagnosis can lead to overestimation of hypertension prevalence, and incorrect treatment 2
- Accurate diagnosis can help identify patients with true resistant hypertension, and those with white coat hypertension 3