The diagnosis of hypertension uses both clinic blood pressure monitoring (CBPM) and ABPM readings (Box 1). If blood pressure measured in the clinic is 140/90 mmHg or higher, a second measurement should be taken during the consultation. If the second measurement is substantially different from the first, take a third measurement. The lower of the last two measurements should be recorded as the clinic blood pressure. Everyone with a clinic blood pressure of 140/90 mmHg or higher should have ABPM to make a diagnosis of hypertension.
Box 1. Hypertension stages
Stage 1 hypertension
Clinic blood pressure ≥140/90 mmHg and subsequent ambulatory blood pressure monitoring (ABPM) or home blood pressure monitoring (HBPM) average blood pressure ≥135/85 mmHg
Stage 2 hypertension
Clinic blood pressure ≥160/100 mmHg and subsequent ABPM or HBPM average blood pressure ≥150/95 mmHg
Severe hypertension
Clinic systolic blood pressure ≥180 mmHg, or clinic diastolic blood pressure ≥110 mmHg
ABPM was identified as the most accurate and cost-effective means of confirming the diagnosis of hypertension. The recommended protocol for ABPM measurements is at least twice hourly during the person's normal waking hours (for example, between 8am and 10pm). The average of at least 14 measurements taken over that period should be used to confirm the diagnosis. If ABPM is unsuitable (for example, in people with atrial fibrillation) or not tolerated, then HBPM is a suitable alternative. Blood pressure should be measured using the average of two readings in the morning and two in the evening, over 4–7 days. The readings on the first day should be discarded.
If blood pressure is ≥180 mmHg and/or 110 mmHg on CBPM, treatment should be considered as soon as possible, before the results of the ABPM are available.
CBPM should be used to monitor the response to treatment in all patients except those who have a discrepancy of ≥20/10 mmHg between clinic and HBPM/ABPM readings, in these patients HBPM or ABPM should be used.
