What are the diagnostic criteria for hypertension?

Diagnostic Criteria for Hypertension

Primary Diagnostic Threshold

Hypertension is diagnosed when systolic blood pressure (SBP) is ≥140 mm Hg and/or diastolic blood pressure (DBP) is ≥90 mm Hg on repeated office measurements, typically requiring 2-3 visits at 1-4 week intervals to confirm the diagnosis. 1

However, there is important divergence between major guidelines that affects clinical practice:

Two Competing Diagnostic Standards

International/European Standard:

• Hypertension is defined as BP ≥140/90 mm Hg 1
• This threshold is endorsed by the International Society of Hypertension, European guidelines, and most international bodies 1, 2

American Standard:

• The ACC/AHA defines hypertension as BP ≥130/80 mm Hg 3, 4
• This lower threshold reclassified an additional 14% of the US population as hypertensive, though only 1.9% required new drug therapy 3
• Stage 1 hypertension: 130-139/80-89 mm Hg 3
• Stage 2 hypertension: ≥140/90 mm Hg 3

Proper Measurement Protocol

Office/Clinic Measurement Requirements:

• Patient must sit quietly for 3-5 minutes before measurement in a comfortable temperature room 1
• No smoking, caffeine, or exercise for 30 minutes prior; empty bladder 1
• Arm supported at heart level on a table, back supported, legs uncrossed, feet flat on floor 1, 3
• Use validated electronic (oscillometric) upper-arm cuff device with appropriate cuff size 1
• Take 3 measurements with 1 minute between them; average the last 2 readings 1
• If first reading is <130/85 mm Hg, no further measurement needed at that visit 1

Multiple Visit Confirmation:

• Diagnosis requires BP measurements from 2-3 separate office visits 1, 3
• Visits should be spaced 1-4 weeks apart depending on BP severity 1
• Exception: Diagnosis can be made on a single visit if BP is ≥180/110 mm Hg AND there is evidence of cardiovascular disease 1, 3

Out-of-Office Confirmation

Home or ambulatory BP monitoring should be used to confirm the diagnosis whenever possible to detect white coat hypertension (elevated office BP but normal out-of-office BP) or masked hypertension (normal office BP but elevated out-of-office BP). 1, 3

• White coat hypertension: Office BP ≥130/80 mm Hg but out-of-office BP <130/80 mm Hg 3
• Masked hypertension: Normal office BP but elevated out-of-office BP 3

Critical Measurement Pitfalls to Avoid

Common errors that bias readings upward and lead to over-diagnosis: 3

• Incorrect arm position (not at heart level)
• Wrong cuff size (too small overestimates BP) 1
• Talking during measurement
• Unsupported back or feet
• Full bladder
• Recent caffeine, smoking, or exercise

Bilateral arm measurement:

• Measure BP in both arms at initial evaluation, preferably simultaneously 1
• Use the arm with higher BP for subsequent measurements if difference is consistently >10 mm Hg 1
• If difference is >20 mm Hg, consider further vascular investigation 1

Special Populations

Elderly patients (≥65 years):

• Diagnostic criteria remain the same (≥140/90 mm Hg by international standards or ≥130/80 mm Hg by ACC/AHA) 3, 5
• Measure standing BP after 1 minute in treated hypertensives to detect orthostatic hypotension 1

Patients with diabetes:

• Same diagnostic threshold applies (≥130/80 mm Hg by ACC/AHA criteria) 3

Clinical Significance

Stage 1 hypertension (130-139/80-89 mm Hg by ACC/AHA criteria) carries approximately 2-fold increased cardiovascular disease risk compared to normal BP. 3 This underscores why the American guidelines lowered the diagnostic threshold, though the ≥140/90 mm Hg standard remains the international consensus and is more practical for resource-limited settings. 1