How to diagnose white coat hypertension?

Evaluating White Coat Syndrome

To diagnose white coat hypertension, a combination of office blood pressure measurements and out-of-office monitoring using either home blood pressure monitoring (HBPM) or ambulatory blood pressure monitoring (ABPM) is required. 1

Definition and Significance

White coat hypertension (WCH) is defined as:

• Elevated blood pressure in the medical setting (≥140/90 mmHg)
• Normal blood pressure when measured outside the office (<135/85 mmHg)
• Occurs in approximately 20% of patients diagnosed with hypertension based on office readings 1, 2

The "white coat effect" refers to the difference between office BP and out-of-office BP measurements, which can be attributed to anxiety, a hyperactive alerting response, or a conditioned response to the medical environment 1.

Diagnostic Algorithm

1. Initial Suspicion:

   • Consider WCH in patients with office SBP >130 mmHg but <160 mmHg or DBP >80 mmHg but <100 mmHg without evidence of target organ damage 1
   • More common in women, elderly patients, and those with mild hypertension 3

2. Confirmation Testing:

   • Home Blood Pressure Monitoring (HBPM):

     • Take at least 2 morning and 2 evening readings daily for 7 days
     • Discard the first day's readings (habituation period)
     • Calculate average of remaining 12+ readings 1
     • Normal HBPM: <135/85 mmHg 1

   • Ambulatory Blood Pressure Monitoring (ABPM):

     • Gold standard for confirming diagnosis 1
     • Normal daytime ABPM: <135/85 mmHg
     • Pay attention to first hour and last hour readings, as these may still show white coat effect 4

3. Interpretation:

   • If office BP ≥140/90 mmHg and HBPM or ABPM <135/85 mmHg → White coat hypertension
   • If both office and out-of-office BP elevated → Sustained hypertension
   • If office BP normal but out-of-office BP elevated → Masked hypertension 1

Follow-up Protocol

For patients diagnosed with white coat hypertension:

• Confirm diagnosis within 3-6 months 1
• Implement periodic monitoring with HBPM or ABPM to detect transition to sustained hypertension 1
• Schedule follow-up every 6 months for office BP and annually for ABPM or HBPM 2, 3
• Monitor for development of target organ damage 1
• Note that WCH converts to sustained hypertension at a rate of 1-5% per year 2

Clinical Pearls and Pitfalls

1. Do not rely on clinical examination alone to diagnose white coat hypertension - confirmation with out-of-office measurements is essential 1

2. HBPM has good specificity (88.6%) but moderate sensitivity (68.4%) for detecting white coat hypertension compared to ABPM 1

3. Beware of masked hypertension - normal office readings but elevated out-of-office readings - which carries similar cardiovascular risk as sustained hypertension 1, 5

4. Long-term prognosis of white coat hypertension is generally better than sustained hypertension but may not be completely benign, especially with longer follow-up periods 1, 3

5. Proper measurement technique for home monitoring is crucial:

   • Seated position with back and arm supported
   • 5 minutes of rest before measurement
   • Two measurements 1-2 minutes apart
   • Use of validated, memory-equipped devices 1

By systematically evaluating patients with suspected white coat hypertension using both office and out-of-office measurements, clinicians can avoid unnecessary treatment while ensuring appropriate monitoring of these patients for potential progression to sustained hypertension.