Blood test may help detect schizophrenia

By Robin McKie

LONDON (DPA): Scientists have revealed they can detect differences in levels of the brain chemical dopamine - closely linked to schizophrenia - in individuals' blood streams. The researchers claim the test is sufficiently accurate to pinpoint whether that blood came from a schizophrenic or a healthy individual.

"We were able to differentiate between blood taken from 14 schizophrenics and a group of 10 people who were unaffected by the disease," said Professor Sara Fuchs, of the Weizmann Institute in Israel. "However, we have to make sure this is a reliable indicator of the disease before we can go any further, and have now launched trials on a much bigger sample."

At present, diagnoses of schizophrenia are based on observations of patients' behavior. Typically, they feel their lives are being controlled, and their thoughts directed by others. They hear voices and can form delusions about the world around them.

Just 1 per cent of the population suffer from the condition, which is known to involve the activity of dopamine, a chemical involved in communications between nerve cells. Dopamine locks on to receptor molecules on brain cells and directs their behavior. The more dopamine receptor cells that a person has, the more likely that person is to have developed schizophrenia, researchers have found.

"However, it is virtually impossible to count the dopamine receptors in a person's head," added immunologist Fuchs, whose team's study is published in the current Proceedings of the National Academy of Sciences. "The only way would be to remove their brain cells, and count their receptors - which is not really practical."

However, the discovery that dopamine receptors are also found on the surfaces of white cells, which circulate in our bloodstream and help protect the body from invading bacteria and other microbes, has opened up new prospects for medical researchers.

"Isolating white blood cells is a lot easier than sampling brain cells of living people," said Fuchs. "But counting dopamine receptors is still tricky." So the Weizmann team analyzed the genetic material that controls the making of receptors instead - and found a significant difference in one particular type, known as D3 receptors.

It was found schizophrenics had, on average, more than three times the amounts of dopamine of healthy individuals, with levels varying from between 2.4 to 7.1.

Pinpointing mental status from blood could be a powerful tool in dealing with psychiatric illnesses. But Fuchs warned the technique would have to be rigorously tested before being brought into widespread use. In particular, there could be a danger if tests gave too many false positives, labeling individuals as schizophrenic when they were actually unaffected by mental illness.

"It's unlikely to be used to screen populations to uncover potential schizophrenics," added Fuchs. "It is unlikely to be accurate enough. However, it can take psychiatrists months to use behavioral criteria to diagnose the disease. This test could cut that dramatically."