What are the guidelines for confirming a diagnosis of hypertension in adults?

Confirmation of Hypertension in Adults

To confirm hypertension in adults, obtain an average of at least 2 office blood pressure readings on at least 2 separate occasions, then confirm the diagnosis with out-of-office monitoring using either ambulatory blood pressure monitoring (ABPM) or home blood pressure monitoring (HBPM) before initiating treatment. 1

Initial Office Screening

The diagnostic process begins with proper office blood pressure measurement technique:

• Patient must be seated quietly for ≥5 minutes with back supported, feet flat on floor, legs uncrossed, and arm supported at heart level 1, 2
• Ensure the patient has emptied their bladder and avoided caffeine, exercise, and smoking for at least 30 minutes before measurement 1
• Use a validated, calibrated device with appropriate cuff size (bladder should encircle 80% of the arm) 1
• Take at least 2 readings separated by 1-2 minutes and use the average 1
• At the first visit, measure blood pressure in both arms and use the arm with the higher reading for subsequent measurements 1

Diagnostic Thresholds

Hypertension is defined using the 2017 ACC/AHA classification system:

• Stage 1 Hypertension: 130-139 mmHg systolic OR 80-89 mmHg diastolic 3, 4
• Stage 2 Hypertension: ≥140 mmHg systolic OR ≥90 mmHg diastolic 3, 4
• Elevated BP (not hypertension): 120-129 mmHg systolic AND <80 mmHg diastolic 3

Mandatory Out-of-Office Confirmation

The USPSTF identifies ABPM as the reference standard for confirming hypertension diagnosis, as it eliminates white coat hypertension (which affects 15-30% of patients with elevated office readings) and detects masked hypertension 1, 5

When to Use Out-of-Office Monitoring:

• For all patients with elevated office readings before starting treatment (Class I recommendation) 1, 5
• Particularly important when office BP is 130-159/80-99 mmHg to screen for white coat hypertension 1, 2

ABPM Diagnostic Thresholds:

• Daytime average: ≥135/85 mmHg 1, 2
• Nighttime average: ≥120/70 mmHg 1, 2
• 24-hour average: ≥130/80 mmHg 1, 2

HBPM Diagnostic Thresholds:

• Average ≥135/85 mmHg confirms hypertension 1
• Patients should take at least 2 readings, 1 minute apart, both morning and evening 1, 2
• Measure daily for at least 1 week, ideally beginning 2 weeks after any treatment changes 2
• Avoid smoking, caffeine, or exercise within 30 minutes before measurements 1

Critical Pitfalls to Avoid

White coat hypertension occurs when office BP is elevated but out-of-office readings are normal—these patients have cardiovascular risk similar to normotensive individuals and should not be treated with medications 4. This is why confirmation with ABPM or HBPM is mandatory before diagnosis 1.

Masked hypertension occurs when office BP appears normal (120-129/75-79 mmHg) but out-of-office readings are elevated—these patients have cardiovascular risk equivalent to sustained hypertension 4. Screen for this with HBPM or ABPM in patients with borderline office readings, especially those with target organ damage or high cardiovascular risk 1, 2.

Single-visit diagnosis significantly overestimates true prevalence by 12.6% 6. Never diagnose hypertension based on measurements from only one office visit 6, 5.

Algorithmic Approach

1. First office visit: Obtain properly measured BP readings (average of ≥2 readings) 1
2. Second office visit (separate occasion): Repeat properly measured BP readings 1, 6
3. If both visits show BP ≥130/80 mmHg: Proceed to out-of-office confirmation 1
4. Order ABPM or HBPM before initiating treatment 1, 5
5. Confirm diagnosis only if out-of-office readings meet diagnostic thresholds (ABPM daytime ≥135/85 mmHg or HBPM ≥135/85 mmHg) 1, 2

When to Screen for Secondary Hypertension

After confirming essential hypertension, screen for secondary causes when: resistant hypertension is present, hypertension onset is abrupt or in young adults, spontaneous hypokalemia occurs, or physical exam reveals abdominal bruits or other suggestive findings 1, 4.