What are the diagnostic criteria for hypertension?

Hypertension Diagnosis Criteria

Hypertension is diagnosed when blood pressure measured in 2-3 office visits is ≥140/90 mmHg, or when out-of-office measurements confirm elevated blood pressure with home BP ≥135/85 mmHg or 24-hour ambulatory BP ≥130/80 mmHg. 1

Blood Pressure Measurement Protocol

Office Measurement

• Use validated automated upper arm cuff device with appropriate cuff size 2, 1
• Measure in a quiet room with comfortable temperature
• Patient should:
  • Avoid smoking, caffeine, and exercise for 30 minutes before measurement
  • Have an empty bladder
  • Be seated with back supported, feet flat on floor, legs uncrossed
  • Have arm resting on table at heart level 1
• At first visit, measure BP in both arms; use the arm with higher BP for subsequent measurements 2
• Take at least 2 readings, 1-2 minutes apart, and use the average 2

Diagnostic Algorithm

1. Initial Screening BP Reading:

   • If BP <130/85 mmHg: Remeasure after 3 years (for adults <40 years) 2
   • If BP 130-139/85-89 mmHg (elevated/high-normal): Confirm with out-of-office measurements 2
   • If BP 140-159/90-99 mmHg: Confirm with out-of-office measurements within 1 month 2
   • If BP 160-179/100-109 mmHg: Confirm as soon as possible (within 1 month) preferably with out-of-office measurements 2
   • If BP ≥180/110 mmHg: Exclude hypertensive emergency and confirm promptly (within a week) 2

2. Confirmation Methods (in order of preference):

   • Ambulatory BP monitoring (ABPM): Diagnostic threshold ≥130/80 mmHg for 24-hour average 2, 1
   • Home BP monitoring (HBPM): Diagnostic threshold ≥135/85 mmHg 2, 1
   • If out-of-office measurements not feasible: Repeated office measurements on multiple visits 2

Special Considerations

White Coat Hypertension

• Elevated office BP but normal out-of-office BP
• Affects 10-30% of patients
• Requires lifestyle modification and regular follow-up 1

Masked Hypertension

• Normal office BP but elevated out-of-office BP
• Affects 10-15% of patients
• May require pharmacological treatment 1

Common Pitfalls to Avoid

1. Single-visit diagnosis: Diagnosing hypertension based on a single visit can overestimate prevalence by approximately 12.6% 3. Multiple visits are essential for accurate diagnosis.

2. Improper measurement technique: Using wrong cuff size (small cuff overestimates BP, large cuff underestimates it), not allowing patient to rest, or incorrect positioning can lead to inaccurate readings 1.

3. Ignoring out-of-office measurements: Office readings alone may not reflect true BP due to white coat effect or masked hypertension 1, 4.

4. Neglecting BP variability: Blood pressure varies significantly during the day and between days, which should be considered when making a diagnosis 1.

5. Failure to recognize severe hypertension: BP ≥180/110 mmHg requires prompt evaluation for hypertensive emergency with assessment for end-organ damage 5.

The most recent guidelines strongly recommend using out-of-office measurements (ABPM or HBPM) to confirm hypertension diagnosis, as these methods provide more reproducible results and correlate better with cardiovascular risk and target organ damage 2, 1.