Flawed blood test widely used by NHS may be wrongly diagnosing thousands of patients with a heart attack
- The test measures for troponin – a protein released during a heart attack
- Researchers analysed thousands of patients receiving treatment in hospital
- They discovered that one in 20 had abnormally high troponin levels
- However, the majority of those showed no signs of having had a heart attack
Thousands of patients may be being wrongly diagnosed with heart attacks in NHS hospitals because of a flawed test.
A blood test for troponin – a protein released into the blood during a heart attack – is widely used in A&E to check whether someone has suffered a heart attack.
Researchers analysed thousands of patients receiving treatment in hospital and found one in 20 had abnormally high troponin levels.
However, the majority of those showed no signs of having suffered a heart attack – despite their tests results suggesting they had.
Cardiologists now fear many patients are being misdiagnosed and unnecessarily undergoing invasive surgery as a result.
Researchers analysed thousands of patients receiving treatment in hospital and found one in 20 had abnormally high troponin levels. However, the majority of those showed no signs of having suffered a heart attack – despite their tests results suggesting they had
NHS guidelines recommend patients undergo a procedure to widen an artery almost immediately, to boost their chances of survival.
Around 190,000 people have a heart attack, known as a myocardial infarction, in the UK each year, according to estimates.
A heart attack, different to a cardiac arrest, occurs when there is an arterial blockage to the organ. The main symptom is chest pain.
Current guidelines recommend troponin tests to help exclude or diagnose a heart attack. They are not used as the sole diagnosis method.
Researchers analysed the troponin levels of 20,000 patients undergoing blood tests at University Hospital Southampton over three months.
Slightly more than five per cent of the patients had a troponin level greater than 40 ng/L – considered to be an indicator of a heart attack.
However, most of the patients were being treated and assessed by hospital staff for other issues, and had no obvious signs of a heart attack.
Professor Nick Curzen, author of the study, published in the British Medical Journal, hopes the findings will stop thousands being misdiagnosed.
He said medical staff need ‘to interpret troponin levels carefully in order to avoid misdiagnosis of a heart attack and inappropriate treatment’.
Professor Curzen added: ‘If it is measured in patients without a classic heart attack presentation, the level may appear raised.
‘And such patients may end up being incorrectly diagnosed as having had a heart attack.
‘They may then receive inappropriate treatment which could be potentially harmful outside of this context.’
A heart attack is the main suspicion when a patient’s troponin levels are abnormally high, or above the 99th percentile.
The 99th centile of troponin for all patients in the study was 296 ng/L – seven times higher than currently considered to be an indicator of a heart attack.
Professor Sir Nilesh Samani, medical director at the British Heart Foundation, also urged doctors to not assume high troponin levels are down to a heart attack.
He said: ‘Troponin measurements are widely used in patients suspected of having a heart attack because troponin is released from the heart when it is damaged.
‘However, the heart can release troponin when a patient is ill from other conditions and not necessarily due to a heart attack.
‘As this study emphasises, a positive test should not always be interpreted as being due to a heart attack.’
Sir Nilesh added: ‘Other information should be taken into account – for example, a patients symptoms and the results of other tests including an ECG.’