Blood pressure readings should be taken from both arms instead of one, scientists say.
Millions of cases of hypertension could be being missed by how doctors currently test for it, experts fear.
High blood pressure can trigger heart attacks and stroke, two of the world’s biggest killers.
A study of more than 50,000 adults analysed the difference between taking blood pressure measurements from two arms, compared to just one.
When both readings were taken, 12 per cent of patients who were originally given the all-clear were reclassified as having high blood pressure.
Blood pressure readings should be taken from both arms instead of one, scientists say
Lead researcher Dr Christopher Clark, a medic at the University of Exeter in Devon, said: ‘High blood pressure is a global issue and poor management can be fatal.
‘Failure to measure both arms and use the higher reading will not only result in under diagnosis and treatment of high blood pressure but also underestimation of risks for millions of people worldwide.
‘It’s impossible to predict the best arm as some people have a higher reading in their left arm compared to right and equal numbers have the opposite.
‘Therefore, it’s important to check both arms.’
He added: ‘Detecting high blood pressure correctly is a vital step towards giving the right treatment to the right people.’
The study, published in the medical journal Hypertension, analysed data from 53,172 participants.
All the volunteers had blood pressure readings taken from their left and right arm, as opposed to just one.
Blood pressure describes the strength with which your blood pushes on the sides of your arteries, and is measured in millimetres of mercury (or mmHg).
Systolic (the top number) reflects the heart’s force when it pumps out blood through the body. Meanwhile, diastolic (the bottom) measures pressure when the heart rests between beats.
If either figure is too high, this can place a strain on the arteries and major organs.
Doctors care more about the systolic number, however.
Dr Clark and colleagues discovered there was an average difference of 6.6mmHg in systolic pressure between arms.
When both readings were taken into account, nearly 6,500 participants were moved into the hypertension category — defined as above 140mmHg.
Differences between arms can be caused by blocked arteries.
Although international guidelines advise checking blood pressure in both arms, the practice is currently not widely adopted in clinics.
Only around half of doctors take readings from both arms, usually because of time restraints in busy clinics or hospitals, experts say.
HIGH BLOOD PRESSURE
High blood pressure, or hypertension, rarely has noticeable symptoms. But if untreated, it increases your risk of serious problems such as heart attacks and strokes.
More than one in four adults in the UK have high blood pressure, although many won’t realise it.
The only way to find out if your blood pressure is high is to have your blood pressure checked.
Blood pressure is recorded with two numbers. The systolic pressure (higher number) is the force at which your heart pumps blood around your body.
The diastolic pressure (lower number) is the resistance to the blood flow in the blood vessels. They’re both measured in millimetres of mercury (mmHg).
As a general guide:
If your blood pressure is too high, it puts extra strain on your blood vessels, heart and other organs, such as the brain, kidneys and eyes.
Persistent high blood pressure can increase your risk of a number of serious and potentially life-threatening conditions, such as: