Alison Motluk
A simple skin patch might soon help psychiatrists identify people with schizophrenia – a diagnosis that can be very difficult to make. The developers of the test also hope that it will help sufferers accept that they need medication.
The “niacin skin flush test” consists of a plastic strip bearing squares of absorbent paper. The paper is impregnated with solutions of methyl nicotinate, a derivative of the B vitamin niacin. When placed on a healthy person’s skin, the solution causes the blood vessels to dilate, turning the skin red. But the skin of schizophrenics reacts weakly.
The healthy flushing response to niacin depends on the release of prostaglandin D2, a compound derived from arachidonic acid, which is found in cell membranes. Studies have shown schizophrenics’ cell membranes to have reduced levels of arachidonic and other essential fatty acids.
Pauline Ward, Iain Glen and colleagues at the Craig Dunain Hospital in Inverness, Scotland, have tested the strip on 38 schizophrenics and 22 healthy volunteers. They applied the strip firmly on the inner forearm, left it for five minutes, then scored the redness on a four-point scale.
The greatest difference between the two groups emerged when the paper was impregnated with a solution of methyl nicotinate. In this test 83% of the schizophrenics had almost no redness, while only 23% of the others failed to react, the researchers note in a paper to appear in a future issue of Schizophrenia Research.
The number of false positives and false negatives is still too high for the test to be an effective diagnostic tool. But the researchers believe it can be refined.
“We are still playing about with the dilutions and exposure times,” Ward says.
Some other schizophrenia researchers do not share the Inverness team’s view that membrane fatty acids are central in schizophrenia. “It’s not getting at the major biochemical abnormalities,” argues Robert Kenwin of the Institute of Psychiatry in London.
But if the researchers are able to refine their test to produce fewer false positives and false negatives, they argue that it could help doctors tackle a vital problem in treating people with the condition – namely, getting them to take their drugs. Showing sufferers that they have a biochemical problem that requires treatment might just convince them of the need.
– This article is excerpted from New Scientist