How is hypertension diagnosed?

How High Blood Pressure is Diagnosed

Hypertension is diagnosed when office blood pressure measurements of ≥140/90 mm Hg are confirmed across 2-3 separate visits taken at 1-4 week intervals, with out-of-office confirmation strongly recommended to exclude white coat hypertension. 1, 2, 3

Office Blood Pressure Measurement Technique

The accuracy of diagnosis depends entirely on proper measurement technique. Before measurement, patients must avoid smoking, caffeine, and exercise for 30 minutes, empty their bladder, and sit quietly for 3-5 minutes in a comfortable room. 1, 2

Proper positioning is critical:

• Patient seated with arm resting on table at heart level 1, 2
• Back supported on chair, legs uncrossed, feet flat on floor 1, 2
• Neither patient nor staff should talk during measurement 1, 2

Measurement protocol:

• Use a validated electronic (oscillometric) upper-arm cuff device with appropriate cuff size covering 75-100% of arm circumference 1, 2
• Take 3 measurements with 1-minute intervals between each 1, 2
• Calculate the average of the last 2 measurements 1, 2
• Initially measure both arms; if difference >10 mm Hg, use the arm with higher readings 2
• Measure standing blood pressure in elderly or diabetic patients to exclude orthostatic hypotension 2

Confirming the Diagnosis

The number of visits required depends on blood pressure severity:

• Usually 2-3 office visits at 1-4 week intervals are needed 1, 2, 3
• For borderline cases (systolic 140-160 mm Hg or diastolic 90-100 mm Hg), measurements on 4-5 separate occasions are recommended 2
• Diagnosis can be made on a single visit only if blood pressure is ≥180/110 mm Hg AND there is evidence of cardiovascular disease 1, 2, 3

Out-of-Office Blood Pressure Confirmation

Out-of-office measurements should confirm the diagnosis whenever possible because they are more reproducible than office measurements and correlate better with target organ damage. 2, 3 This is particularly important for borderline cases to identify white coat hypertension (elevated only in office) or masked hypertension (normal in office but elevated at home). 1, 2

Two methods are available:

• Home blood pressure monitoring (HBPM): Diagnostic threshold >135/85 mm Hg 2, 3
• 24-hour ambulatory monitoring (ABPM): Diagnostic threshold >125/80 mm Hg 2, 3

For home monitoring, take at least 2 morning and 2 evening readings daily for 1 week, discarding the first day's readings (total of 12 readings for clinical decisions). 1

Initial Evaluation After Confirming Hypertension

Mandatory laboratory tests include: 2, 3

• Serum creatinine and estimated glomerular filtration rate (eGFR) 2, 3
• Serum sodium and potassium 2, 3
• Fasting blood glucose 2, 3
• Lipid profile (at least total and HDL cholesterol) 2, 3
• Urinalysis with dipstick for protein and blood 2, 3
• 12-lead ECG to detect left ventricular hypertrophy, atrial fibrillation, or ischemic heart disease 1, 2, 3

Physical examination should assess for: 1

• Pulse rate, rhythm, and character 1
• Jugular venous pressure 1
• Apex beat and extra heart sounds 1
• Basal crackles and peripheral edema 1
• Vascular bruits (carotid, abdominal, femoral) and radio-femoral delay 1
• Enlarged kidneys, increased BMI/waist circumference, enlarged thyroid 1

Blood Pressure Classification

Category	Systolic (mm Hg)	Diastolic (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

2

Critical Pitfalls to Avoid

Never diagnose hypertension based on a single office visit measurement (except when BP ≥180/110 mm Hg with cardiovascular disease evidence). 2, 3 This is the most common diagnostic error.

Other critical errors include:

• Using incorrect cuff size (too small overestimates, too large underestimates blood pressure by >15 mm Hg) 2, 3, 4
• Failing to allow adequate 3-5 minute rest period before measurement 2, 3
• Talking during blood pressure measurement 2, 3
• Not confirming borderline office readings with out-of-office measurements, missing white coat or masked hypertension 2, 3
• Failing to check standing blood pressure in elderly or diabetic patients 2