Blood Pressure Diagnostic Thresholds
The ACC/AHA 2017 guideline defines hypertension as systolic ≥130 mmHg or diastolic ≥80 mmHg, based on an average of ≥2 readings on ≥2 separate occasions. 1
Blood Pressure Categories (ACC/AHA Classification)
The following categories apply when measurements are properly obtained with validated devices after 5 minutes of quiet rest, back supported, feet flat, and arm at heart level 1:
- Normal BP: <120/<80 mmHg 1
- Elevated BP: 120–129/<80 mmHg 1
- Stage 1 Hypertension: 130–139/80–89 mmHg 1
- Stage 2 Hypertension: ≥140/≥90 mmHg 1, 2
When systolic and diastolic readings fall into different categories, assign the patient to the higher category. 1
Diagnostic Confirmation Requirements
Before initiating antihypertensive medication, confirm the diagnosis with out-of-office blood pressure monitoring (home or 24-hour ambulatory) to exclude white-coat hypertension. 1, 3 This is critical because office-based measurements alone lead to over-diagnosis when proper technique is not followed 1.
The diagnosis requires an average of ≥2 careful readings obtained on ≥2 separate occasions, with readings separated by 1 minute 1, 2. Two readings are sufficient unless the difference between them is ≥10 mmHg for both systolic and diastolic, in which case a third reading should be obtained and all three averaged 4.
European Society of Cardiology Classification (Alternative Framework)
The 2024 ESC guideline retains the traditional 140/90 mmHg threshold for hypertension diagnosis, creating an international divergence from ACC/AHA 1, 3. The ESC categories are 1, 5:
- Optimal BP: <120/70 mmHg 3, 5
- Normal BP: 120–129/70–84 mmHg 1, 3, 5
- High Normal BP (Elevated): 130–139/85–89 mmHg 1, 3, 5
- Grade 1 Hypertension: 140–159/90–99 mmHg 1, 5
- Grade 2 Hypertension: 160–179/100–109 mmHg 1, 5
- Grade 3 Hypertension: ≥180/≥110 mmHg 1, 5
- Isolated Systolic Hypertension: ≥140/<90 mmHg 1, 5
Hypertensive Crisis
A hypertensive crisis is defined as systolic ≥180 mmHg or diastolic ≥120 mmHg. 6, 7, 8 This is further classified into:
- Hypertensive urgency: Severe elevation without acute end-organ damage; treat with oral agents over 24–48 hours 6, 7
- Hypertensive emergency: Severe elevation with acute end-organ damage (cardiac, renal, neurologic, aortic dissection); requires immediate IV therapy in an ICU setting with goal to reduce BP by 20–30% within minutes to hours (except aortic dissection, which requires immediate reduction to <120 mmHg systolic) 6, 7, 9, 8
Critical Measurement Pitfalls to Avoid
Common measurement errors that falsely elevate readings include 1:
- Using an incorrectly sized cuff (too small)
- Applying the cuff over clothing
- Allowing the patient's arm to hang unsupported
- Measuring with a full bladder
- Permitting conversation during measurement
- Allowing legs to be crossed or hanging
These errors bias readings upward and lead to over-diagnosis and over-treatment. 1
Out-of-Office BP Equivalents
For comparison with office readings, the following thresholds are equivalent 1:
| Office BP | Home BP | Daytime Ambulatory | 24-Hour Ambulatory |
|---|---|---|---|
| 130/80 | 130/80 | 130/80 | 125/75 |
| 140/90 | 135/85 | 135/85 | 130/80 |
Home and ambulatory monitoring are essential to detect white-coat hypertension (office BP ≥130/80 but out-of-office <130/80) and masked hypertension (office BP <130/80 but out-of-office ≥130/80). 1