GP academic and specialist in cardiovascular medicine Professor Chris Clark provides an update on current best practice in the management of hypertension, including discussion of blood pressure measurement techniques, current diagnostic and treatment target thresholds, when referral is required and approaches to treatment escalation.
Learning objectives
This module will support your understanding of the best evidence-based approaches to diagnosis and management of hypertension, including:
• Appropriate methods of blood pressure measurement including how to act on between-arm differences.
• Diagnostic thresholds for different stages of hypertension and on-treatment target blood pressure levels.
• When to refer people urgently and what investigations will be required.
• What investigations to do in people under 40 diagnosed with hypertension, and when they should be referred.
• How to monitor, promote and support treatment adherence in those failing to reach BP target levels.
• Current treatment algorithms and how to escalate treatment appropriately.
• Considerations when treating older or frail patients, including testing for postural hypotension.
The information provided, unless otherwise stated, is based on the current NICE guidelines on diagnosis and management of hypertension in adults (NG136), published in 2019 and most recently updated in November 2023.
1. What are the current thresholds for diagnosing hypertension?
Hypertension is the leading modifiable risk factor for cardiovascular deaths worldwide, and represents one of the commonest reasons for primary care consultation. The majority of hypertensive people in the UK are not controlled to target, and as many as half a million may have missed out on appropriate treatment during the COVID-19 pandemic.
The diagnosis and treatment of hypertension requires accurate blood pressure (BP) measurement (see Box 1).
Box 1. Taking accurate BP measurements in primary care
This takes time, which is a precious commodity in primary care. However, poor or hurried measurement techniques generally overestimate rather than underestimate BP, thus exposing more people to repeat measurements and further investigations, and actually increasing overall workload.
Training and regular refreshing of measurement skills is important. Good technique requires the patient to be seated quietly, at rest for 5 minutes with back supported, legs uncrossed and the measurement arm supported at heart level. The measurement cuff should be of appropriate size, selected so that the bladder encircles more than 80% but less than 100% of the arm. Using under-sized cuffs can significantly over-estimate BP so a full range of large and extra-large cuffs should be readily available. So-called ‘white coat effects’ are also important and more often induced by doctors than by nurses or pharmacists; there is, therefore, a strong case for routine clinic BP measurement not being performed by doctors. White coat effects are defined as a discrepancy of 20/10mmHg or more between clinic and ambulatory BP measurements.
Measurement should use a validated (ie, shown to be accurate) BP monitor; the British and Irish Hypertension Society (BIHS) maintains the only independent list of such validated monitors and is recommended by NICE. Any monitor should be regularly recalibrated and serviced according to manufacturer advice. Blood pressure monitors tend to become less accurate as they age. When assessing home readings it is, therefore, important to enquire about patients’ own devices and calibrate them if readings are in doubt.
Initial assessment should measure BP in both arms. Systolic readings can differ by 10mmHg or more between arms in 10% of people with hypertension, and failure to recognise the higher reading arm can misclassify up to 12% of people at the 140mmHg systolic threshold, thus delaying or missing new diagnoses of hypertension. NICE recommends adopting the higher reading arm for all future measurements when the systolic difference between arms remains greater than 15mmHg (found in approximately 4% of people with hypertension in primary care).
However, cardiovascular risk equations and prediction of cardiovascular events and death are more accurate when based on the higher-reading arm, irrespective of the degree of inter-arm difference so initial comparison of arms, and routine adoption of the higher-reading arm, is important for all people. A systolic inter-arm difference of 10mmHg or more is also itself associated with additional cardiovascular risk, which rises with the magnitude of inter-arm difference. This should be taken into account when considering individual treatment decisions based on predicted cardiovascular risk scores.
NICE defines three thresholds for staging hypertension (see Box 2, below).
Blood pressure assessments usually begin with a clinic reading. If the initial reading is higher than 140/90mmHg (the threshold defining stage 1 hypertension), it should be repeated, and if substantially different a third measurement taken. The lower of the second or third readings is recorded as the clinic BP. (Note that NICE differs here in comparison to the practice of recording the average of second and third readings adopted internationally.)
If clinic BP is 140/90mmHg or higher, then confirmation with ambulatory BP monitoring (ABPM) is required. A daytime average BP of 135/85mmHg confirms the diagnosis of hypertension.
Confirmation of a clinic reading with ABPM or home BP monitoring (HBPM) using the appropriate thresholds is recommended because the latter provide better prognostic information and, to some extent, overcome the difficulty of interpreting clinic BP readings elevated by white coat effects.
Box 2. Definitions of Stage 1-3 hypertension
Stage 1 hypertension
Clinic BP ranging from 140/90mmHg to 159/99mmHg and subsequent ABPM daytime average or HBPM average BP ranging from 135/85mmHg to 149/94mmHg.
Stage 2 hypertension
Clinic BP of 160/100 mmHg or higher but less than 180/120mmHg and subsequent ABPM daytime average or HBPM average BP of 150/95mmHg or higher.
Stage 3 or severe hypertension
Clinic systolic BP of 180mmHg or higher or clinic diastolic BP of 120mmHg or higher.
Stage 1 hypertension may initially be managed by a trial of lifestyle changes (essentially weight loss, dietary sodium reduction, alcohol reduction and exercise promotion); progress must be monitored.
For patients aged under 80 years, failure to reduce BP below 140/90mmHg in the clinic should lead to discussion of initiation of antihypertensive drug treatment. Drug treatment is recommended in the presence of:
• target organ damage
• established cardiovascular disease
• renal disease
• diabetes
• estimated 10‑year risk of cardiovascular disease of 10% or more.
For adults aged 80 or over, NICE advises initiating treatment (in addition to lifestyle advice) if clinic BP is over 150/90mmHg (145/85mmHg on ABPM or HBPM) – see questions 6 and 11 below for further details on BP thresholds in older patients specifically.
Stage 2 hypertension requires immediate drug initiation alongside lifestyle interventions.
Home readings (HBPM) can be sought if ambulatory measurement is not tolerated. Although this guidance was introduced in 2011, not all general practices have access to ABPM as the gold standard diagnostic tool for hypertension. This presents an ongoing challenge to commissioners who need to resource good quality hypertension care appropriately. NICE advises that ABPM can be offered as an alternative if HBPM is unsuitable or not tolerated. It is often assumed that HBPM can substitute for diagnosis when ABPM is unavailable, but this is not within NICE’s recommendations and access to HBPM should not be used to justify under-resourcing a BP measurement service. Ideally, commissioners should be ensuring that GP practices are resourced to use ABPM. Whether ABPM or HPBM is used, correct procedures for fitting cuffs, undergoing measurements, and interpreting results are essential. A range of educational resources to support correct measurement can be found on the BIHS website.
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Professor Chris Clark is Associate Professor of Primary Care Cardiovascular Medicine at the Exeter Collaboration for Academic Primary Care (APEx), University of Exeter Medical School. He is a Fellow of the British and Irish Hypertension Society (BIHS) and chairs the BIHS Standing Committee on Blood Pressure Measurement. He was a NICE hypertension guideline committee member until 2023.
