What are the criteria and process for diagnosing hypertension?

Diagnosing Hypertension: Criteria and Process

Hypertension is diagnosed when a person's systolic blood pressure (SBP) in the office or clinic is ≥140 mm Hg and/or their diastolic blood pressure (DBP) is ≥90 mm Hg following repeated examination. 1

Office Blood Pressure Measurement

Standard Protocol

• Measurements should be taken in a quiet room with comfortable temperature 1
• Patient should avoid smoking, caffeine, and exercise for 30 minutes before measurement 1
• Patient should empty bladder and remain seated and relaxed for 3-5 minutes before measurement 1
• Neither patient nor staff should talk during measurements 1
• Patient should be seated with arm resting on table at heart level, back supported, legs uncrossed, and feet flat on floor 1
• Use validated electronic (oscillometric) upper-arm cuff device or calibrated auscultatory device 1
• Ensure appropriate cuff size based on arm circumference 1

Measurement Protocol

• Take 3 measurements with 1 minute between them 1
• Calculate the average of the last 2 measurements 1
• If BP of first reading is <130/85 mm Hg, no further measurement is required 1
• Initially measure BP in both arms; if consistent difference >10 mm Hg, use the arm with higher BP 1
• Standing BP should be measured in elderly or diabetic patients to exclude orthostatic hypotension 1

Confirming the Diagnosis

• Usually 2-3 office visits at 1-4 week intervals are required to confirm hypertension 1
• Diagnosis can be made on a single visit if BP is ≥180/110 mm Hg and there is evidence of cardiovascular disease 1
• For borderline cases (SBP 140-160 mmHg or DBP 90-100 mmHg), more stringent confirmation is recommended with measurements on 4-5 separate occasions 1

Blood Pressure Classification

Category	Systolic BP (mm Hg)	Diastolic BP (mm Hg)
Optimal	<120	<80
Normal	<130	<85
High normal	130-139	85-89
Grade 1 (mild) hypertension	140-159	90-99
Grade 2 (moderate) hypertension	160-179	100-109
Grade 3 (severe) hypertension	≥180	≥110
Isolated systolic hypertension Grade 1	140-159	<90
Isolated systolic hypertension Grade 2	≥160	<90
[1]

Out-of-Office Blood Pressure Measurement

• When available, diagnosis should be confirmed by out-of-office BP measurement 1
• Out-of-office measurements include home blood pressure monitoring (HBPM) and 24-hour ambulatory blood pressure monitoring (ABPM) 1
• Out-of-office measurements are more reproducible than office measurements and more closely associated with hypertension-induced organ damage 1
• These measurements help identify white coat hypertension and masked hypertension 1, 2
• Threshold for hypertension using home BP monitoring is >135/85 mm Hg 1, 2
• Threshold for hypertension using 24-hour ambulatory monitoring is >125/80 mm Hg 1

Indications for Ambulatory Blood Pressure Monitoring

• Unusual variability of blood pressure 1
• Possible white coat hypertension 1, 2
• Evaluation of nocturnal hypertension 1
• Evaluation of drug-resistant hypertension 1
• Determining efficacy of drug treatment over 24 hours 1

Initial Evaluation of Hypertensive Patients

Routine Investigations

• Urine strip test for protein and blood 1
• Serum creatinine and electrolytes 1
• Blood glucose (ideally fasted) 1
• Blood lipid profile (at least total and HDL cholesterol) 1
• Electrocardiogram 1

Assessment of Cardiovascular Risk

• Evaluate for presence of other cardiovascular risk factors 1
• Assess for evidence of target organ damage 1
• Screen for secondary causes of hypertension 1
• Evaluate for comorbid conditions 1

Special Considerations

• Hypertensive emergency (BP ≥180/110 mmHg with evidence of acute end-organ damage) requires immediate treatment 3
• White coat hypertension (elevated office BP but normal out-of-office BP) should be identified to avoid unnecessary treatment 1, 2
• Masked hypertension (normal office BP but elevated out-of-office BP) carries similar risk as sustained hypertension and requires identification 1
• Automated office BP measurement, where multiple readings are taken with the patient alone, may reduce white coat effect 2

Common Pitfalls to Avoid

• Diagnosing hypertension based on a single measurement 1
• Using inappropriate cuff size (too small overestimates, too large underestimates BP) 1
• Failing to allow adequate rest period before measurement 1
• Talking during BP measurement 1
• Not considering white coat or masked hypertension 1, 2
• Neglecting to assess for orthostatic hypotension in elderly or diabetic patients 1