New tests are more accurate

International experts say the most reliable method is to check for a rise in a set of proteins called troponins.

However, some doctors have been slow to switch from conventional ECGs and enzyme tests.

A study by the University of Warwick, published in Heart, found the older methods were far less accurate.

The new methods deliver a more accurate diagnosis in a more timely fashion Dr Steve Smith

The researchers compared the accuracy of heart attack diagnosis in 401 patients with chest pain who were treated at one teaching hospital, using both the conventional and new techniques.

They found 4% of patients had been wrongly diagnosed using the conventional techniques. Some were diagnosed as being healthy when they had in fact had a heart attack, others were told they had suffered a heart attack when they had not.

Almost all of these cases had been admitted by doctors who were not cardiologists.

But when the new methods were applied, the number of people who were identified as having had a heart attack rose by 27%.

Overall, the diagnosis had to be changed in 12% of patients.

Human errors

The researchers found over half of the changed diagnoses could be blamed on the inaccuracy of the old methods.

The rest were down to errors, such as inappropriate interpretation of the results, and a failure to take a full range of samples.

The researchers speculate that part of the problem may be down to inadequate training, staffing, supervision, or the patient being moved to different wards.

But they found that troponin screening was a better way to predict a patient's six-month prognosis.

Enzyme testing was only effective, they said, in conjunction with a troponin test.

They warn that the old methods are unreliable, time consuming, and carry a higher risk of error.

The new methods are not only more accurate, they say, but are also simpler and quicker to use.

The researchers also stress that their study found that patients received better care when treated by a cardiologist, rather than a general physician.

Many have switched

Researcher Dr Steve Smith, told BBC News Online many doctors had switched to the new techniques since the data was collected.

He said: "The new methods deliver a more accurate diagnosis in a more timely fashion.

"This means patients are given the right treatment more quickly and therefore their prognosis is better."

Dr Charmaine Griffiths, of the British Heart Foundation, said the charity had recommended that anyone admitted to hospital with possible cardiac symptoms should be tested for troponin levels.

"Anyone who has a heart attack will have detectable levels of troponins as these proteins are only released following cardiac damage.

"Most patients will show increased levels of troponin 12 hours after hospital admission, if not before."

Dr Griffiths said not everyone who has a heart attack will present with the classic signs, such as severe chest pain and tightness in the neck and jaw.

She said: "Sometimes a heart attack is silent and produces little discomfort."