A fingertip test could detect patients in the earliest stages of heart disease, US scientists have claimed.
The test picked up early indications of heart disease
A study in the Journal of the American College of Cardiology found it detected early signs of disease in patients which conventional tests missed.
The team from the Mayo Clinic said they hoped it would offer a simple way of identifying those at risk.
British heart experts said the study was interesting, but more evidence of the test's effectiveness was needed.
The first signs of heart disease and atherosclerosis - the build-up of fatty materials in the arteries which reduces blood flow - are seen within a layer of cells called the endothelium which line coronary blood vessels.
Its role is to protect vessel walls from injury and help maintain appropriate blood flow and blood pressure.
The researchers wanted to see if these early signs, so-called endothelial dysfunction, could be detected using a non-invasive fingertip test.
The reactive hyperaemia peripheral arterial tonometry (RH-PAT) test uses a probe to measure how the volume of a fingertip changes as blood pulses through it.
One measurement is taken, then a blood pressure cuff is inflated to restrict blood flow to the arm for five minutes.
Another reading is taken once the cuff has been removed to see how quickly vessels in the fingertip respond to the initial rush of blood.
The researchers also carried out angiograms, where a catheter is inserted into an artery and an X-ray picture of the blood vessels taken to show where they are narrowed.
Ninety-four patients took part in the study. The results of this standard test showed none had coronary artery disease.
But the RH-PAT test indicated 55 showed signs of endothelial dysfunction.
The test normally shows a distinct increase after blood flow is restored in the arms of patients, but in affected patients, this response was much more muted.
The researchers said it may one day have a role as an initial test to detect people at risk of developing heart disease.
Dr Amir Lerman, who led the study, said: "In this group of patients with chest pain, the non-invasive test was very sensitive in identifying those with early heart disease.
"Various studies demonstrated that the presence of endothelial dysfunction is an independent risk factor for cardiovascular events.
"Importantly, various interventions, such as treatment of cardiovascular risk factors and certain drugs, including statins, were shown to improve endothelial function.
"Thus, the early detection of endothelial dysfunction may have both prognostic and therapeutic implications."
He added: "The next step is to extend the research to broader populations of patients who may not yet have symptoms.
"Because this is a simple test that takes only about 20 minutes. we hope it could become another screening tool to help us identify and more effectively treat patients with heart disease."
Belinda Linden, a spokesperson for the British Heart Foundation, said: "The evidence is growing that abnormal activity of the blood vessel lining contributes to atherosclerosis.
"Being able to identify early changes within the artery wall would improve prevention of heart disease through effective risk factor control or medications for those who do not yet have symptoms."
But she added: "This method of using blood vessel changes as an indicator of the likelihood of cardiovascular disease is interesting but needs more examination using larger studies and wider groups of people who don't have apparent artery disease."