Blood test for schizophrenia proposed

The gene, known as D3, is associated with an important message-carrying chemical called dopamine, Tal Ilani and colleagues at the Weizmann Institute of Science in Rehovot in Israel, said.

"Dopamine is a major neurotransmitter in the central nervous system and its receptors are associated with a number of neuropathological disorders such as Parkinson’s disease and schizophrenia," the researchers wrote in their report, published in the Proceedings of the National Academy of Sciences.

They cited other research that shows some immune system cells such as lymphocytes carry receptors for Dopamine — little chemical doorways into cells that are used by various chemicals, viruses and by other cells.

So they looked at 14 patients with schizophrenia and 14 people of the same ages and sexes who did not have schizophrenia.

They found that people with schizophrenia tended to have more of a certain class of these receptors, called D3 Dopamine receptors. They did not count the numbers but ran genetic tests that looked for messenger RNA levels — which indicates how hard that particular gene is working.

Patients taking medications and those not taking any drugs both tended to have at least twice as much D3 activity as people without schizophrenia, the researchers said.

"We propose the D3 receptor messenger RNA on blood lymphocytes as a marker for identification and follow-up of schizophrenia," they wrote.

Most drugs that treat schizophrenia act against a related receptor known as D2.

The researchers said more studies will be needed but said they hoped their findings could lead to a blood test for the disease, which affects up to one per cent of the population worldwide.

Schizophrenia is usually diagnosed in early adulthood. It is incurable and the drugs used to treat it often have serious side-effects that make patients reluctant to take them.