By Stephen Adams, Medical Correspondent

About a quarter of people become anxious while they have their blood pressure taken in the surgery, meaning they potentially give a misleading reading. This wrongly pushes many into the high blood pressure zone, a phenomenon known as white coat hypertension. This means up to three million people could be taking drugs needlessly or in incorrect doses.

Now the National Institute for Health and Clinical Excellence (Nice) has produced definitive guidelines so GPs can diagnose the condition more accurately.

They recommend that when a patient is deemed hypertensive in the consulting room, they are sent home with a special machine called an ambulatory blood pressure monitoring (ABPM) device.

This comprises an arm cuff and a small belt-clip monitor box containing a timer, compressor and computer chip, which can be worn during everyday activities.

Patients wear them for 24 hours and readings are automatically taken every half an hour during waking hours. The information is then downloaded on to the surgery computer.

He said ABPM monitoring would help screen out those with white coat hypertension while providing more accurate readings for those who really had high blood pressure, resulting in better treatment.

High blood pressure, which leads to heart disease and stroke, is one of the country’s most widespread health problems. Some 12 million people are officially diagnosed – although a quarter arguably wrongly – while up to six million more could have it without knowing.

Nice has decided to recommend nationwide (England and Wales) use of the ABPM monitors – which currently cost about £1,000 apiece – after doing a financial analysis which showed they would save money in the long term.

The NHS will have to fork out about £5 million a year to invest in the machines, but Nice predicts that after two years they will start to save money due to less prescriptions for ACE inhibitors, calcium-channel blockers and diuretics, which all lower blood pressure.

These drugs currently cost the NHS £1 billion a year, or one per cent of its budget. Cut out people with white coat hypertension and that bill would fall dramatically.

Prof Williams described the new method as a “step-change” that was likely to be replicated worldwide.

He said: “It will ensure that those who really need treatment get treated and those who don’t need treatment don’t get treated unnecessarily.”

Nice estimates that in five years, treatment costs will be £15.6 million lower per annum than today, giving a net saving of £10.5 million in that year.

These estimates are quite conservative because they are based on new diagnoses rather than re-evaluating the 12 million existing ones.

However, Prof Williams believed many people with “borderline” hypertension would now question whether they really needed to be taking drugs and would ask to be re-checked.

“The emphasis is on new diagnoses but, having scaled it up, we will be able to use it for reviewing existing diagnoses,” he said.

At the moment the availability of devices is very limited though, which could lead to long delays for patients.

Currently, only about one diagnosis in 20 is made with an ABPM machine, said Prof Richard McManus, a Birmingham GP, who spearheaded the cost-effectiveness study, published today in The Lancet. He said they were mainly confined to larger GP practices and specialist units.

Questions remain over whether GPs will be convinced enough of the benefits to pay for the devices, which experts admitted were extremely expensive. The Nice guidelines are not mandatory.

Prof Williams believed the cost per device could come down to £500 in time, especially if the NHS ordered sufficient numbers.

A much less expensive option is to use home blood pressure monitoring devices, which cost as little as £15. These non-automated devices require patients to remember to take their pressure every half hour and record the information accurately.

Nice says these can be used in the absence of ABPMs, but Prof Williams emphasised the evidence showed automated devices produced better diagnoses, better outcomes, and were eventually cost effective.

Prof Mark Caulfield, president of the British Hypertension Society, believed the future lay in pared-down ABPM devices that plugged into smartphones, harnessing their processing power.

iHealth, an American company, already makes such a device for iPhones and iPads – albeit without a timer for full automation – which sells for $100 (£60).

*One in seven blood pressure machines used by GPs could be inaccurate, according to a study in the British Journal of General Practice.

A research team from Oxford, led by Dr Christine A’Court, tested machines in over 80 general practices and found 14 per cent did not meet British Hypertension Society standards.

Dr A’Court and her team concluded low cost aneroid machines were particularly inaccurate and should be replaced with digital devices.

http://www.telegraph.co.uk/health/8718355/Home-checks-for-high-blood-pressure.html