Common blood pressure checking errors can push readings higher, experts warn

Thousands of people in Britain could be told they have high blood pressure because of avoidable errors during routine NHS checks, a GP has warned.

NHS advice says patients should be seated upright with their arm supported on a table while the measurement is taken.

However, specialists say that guidance is not always followed in busy clinics, increasing the chance of misleading results and wrong diagnoses.

“Accurate blood pressure measurement is essential if we are to correctly identify and treat people at risk of damage from high blood pressure,” Dr Dean Eggitt, an NHS GP, told the Daily Mail.

“Over-treatment and medication-induced side effects can cause real harm, particularly in vulnerable patients.

“Poor technique can ultimately result in inappropriate treatment decisions and reduce quality of life.”

The warning comes after a recent US study found that arm position can make a major difference to blood pressure readings.

Researchers at Johns Hopkins Medicine found that letting an arm hang unsupported by a patient’s side raised systolic blood pressure — the top number in a reading — by nearly 7 mmHg.

Resting the arm on the lap also led to this figure being overstated by almost 4mmHg.

Experts said the findings support NHS guidance that a patient’s arm should be placed on a table or desk at heart level when blood pressure is checked.

High blood pressure affects around one in three adults in England and raises the risk of stroke, heart attack, kidney disease and even dementia.

Because it often causes no symptoms, it can go unnoticed until it is too late.

More than four million people in England are believed to have the condition without realising it.

The findings, published in the journal JAMA Internal Medicine, came amid updated American Heart Association guidance that puts greater emphasis on accurate blood pressure measurement when monitoring the condition at home.

Patients are also advised to sit quietly for at least five minutes before a reading, keep both feet flat on the floor and support their back. The middle of an adjustable cuff should sit at mid-heart level, with the arm resting on a desk or table.

In the study, researchers from Johns Hopkins Medicine measured the blood pressure of 133 adults aged 18 to 80.

Before the readings, all participants walked for two minutes — to mimic arriving at a doctor’s appointment — and then sat quietly for five minutes.

They were fitted with an upper-arm blood pressure cuff and given a series of measurements 30 seconds apart.

The results suggested people could be diagnosed with hypertension simply because of arm position, with the highest readings recorded when the arm hung at the side.

That position overstated systolic pressure by 6.5mmHg and diastolic pressure by 4.4mmHg.

The researchers said the differences were large enough to influence whether some patients crossed the threshold for a hypertension diagnosis.

According to the NHS, normal blood pressure ranges from 90/60mmHg to 120/80mmHg.

High blood pressure is defined as anything above 135/85mmHg for a home reading, or 140/90mmHg and above when measured by a healthcare professional at a pharmacy, GP surgery or hospital.

The warning follows separate analysis from the University of Oxford suggesting that more than half of people with high blood pressure do not know they have it, leaving them at greater risk of early death.

Researchers also estimated that only half of those treated for the condition by their GP have their blood pressure under control.

The authors said current National Institute for Health and Care Excellence (NICE) guidance means many cases are never identified, treated or brought under control.

They argued that existing diagnostic routes can create a “leaky cascade of care”, with some patients never receiving a diagnosis or effective treatment.