What are the diagnostic criteria for hypertension (high blood pressure)?

From the Guidelines

Hypertension is diagnosed when a person has consistently elevated blood pressure readings over multiple visits, with a systolic pressure of 130 mmHg or higher, or a diastolic pressure of 80 mmHg or higher, as recommended by the 2020 international guidelines 1. To diagnose hypertension, a healthcare provider will measure blood pressure on at least two separate occasions, typically 1-4 weeks apart, using a blood pressure cuff (sphygmomanometer).

Key Considerations for Accurate Measurement

• Patients should avoid caffeine, exercise, and smoking for 30 minutes before measurement
• Sit with back supported and feet flat on the floor
• Rest quietly for 5 minutes before the reading
• Multiple measurements should be taken during each visit, with the arm positioned at heart level

Additional Diagnostic Tools

• Home blood pressure monitoring may also be recommended, using an automated device to take readings twice daily (morning and evening) for 7 days
• 24-hour ambulatory blood pressure monitoring might be used to detect white coat hypertension (elevated readings only in clinical settings) or masked hypertension (normal readings in clinical settings but elevated elsewhere)

Importance of Accurate Diagnosis

These diagnostic steps are crucial because hypertension often has no symptoms but significantly increases the risk of heart disease, stroke, and kidney damage if left untreated, as highlighted in the 2018 American College of Cardiology/American Heart Association hypertension guideline 1 and further supported by the 2020 Trends in Cardiovascular Medicine article 1.

Classification of Blood Pressure

The classification of blood pressure is as follows:

• Normal BP level: <130/85mmHg
• High-normal BP level: 130-139/85-89mmHg
• Hypertension BP level: ≥140/90mmHg, as outlined in the 2020 international guidelines 1.

From the Research

Diagnosis of Hypertension

To diagnose hypertension, the following methods can be used:

• Office blood pressure (BP) measurements: although not the most accurate method, it can be used as an initial assessment 2
• Home blood pressure monitoring (HBPM): a more accurate method than office BP measurements, with a sensitivity of 75% and specificity of 76% 2
• 24-hour ambulatory blood pressure monitoring (ABPM): considered the reference standard for BP assessment, with a sensitivity and specificity that can vary depending on the threshold values used 2

Blood Pressure Measurement

Blood pressure should be measured on at least two separate occasions to confirm a diagnosis of hypertension 3. The following are recommended:

• Measure blood pressure at least twice, with a interval of time between measurements 3
• Use validated automated oscillometric devices for HBPM and ABPM 4
• Take multiple blood pressure readings at specific times during the day and evening over a long period for HBPM 4
• Perform ABPM using standard techniques to minimize user errors 4

Threshold Values

The following threshold values can be used to diagnose hypertension:

• Office BP: ≥140/90 mm Hg 2
• HBPM: ≥135/85 mm Hg 2
• ABPM: 24-hour mean BP ≥130/80 mm Hg or mean BP while awake ≥135/85 mm Hg 2

Limitations of Office BP Measurements

Office BP measurements have limitations, including:

• May not be accurate enough to rule in or rule out hypertension 2
• Can lead to misdiagnosis and mistreatment if used alone 4
• May not reflect the patient's true blood pressure levels outside of the office setting 4