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A BLOOD test could reveal if someone is going to develop Parkinson’s years
before symptoms appear, say researchers in Australia. It could also give us more
clues about the causes of the disorder.

At the moment, Parkinson’s can be diagnosed only after signs such as
slowness, stiffness and tremor appear. Even then, a post-mortem examination of
the brain is needed for a definite diagnosis.

These symptoms are caused mainly by the loss of dopamine-producing nerve
cells in a part of the brain that controls movement. The new test looks for the
presence of antibodies that mop up neuromelanin, one of the substances that is
released by the cells as they degenerate.

The test was developed by a team led by Kay Double of the Prince of Wales
Medical Research Institute in Sydney. The researchers have been awarded a
provisional patent, and will present their results in March at a conference on
Parkinson’s in Kyoto, Japan.

The root cause of Parkinson’s remains unclear, but the neuromelanin
antibodies might be involved, says neurologist Dominic Rowe of the Royal North
Shore Hospital in Sydney, another member of the team. “The antibodies might be
involved directly in the neuronal degeneration, or they may be a response to the
disease process. They might be step 3, they might be step 99. Either way,
understanding the biology is the first step towards finding a treatment.”

So far, the blood test has only been put through its paces in patients who
have clear symptoms. “It’s about 80 per cent accurate,” says Glenda Halliday of
the Prince of Wales Medical Research Institute, who is also a team member.

The dopamine-producing neurons are believed to start degenerating 7 to 20
years before a person gets sick, so the next step will be to see whether the
test can spot Parkinson’s before symptoms occur. “The `ifs’ all concern whether
it will be a good predictor test,” says Malcolm Horne, a neurologist at Monash
University in Melbourne.

“If it is, it will be quite good for telling us about the natural history of
the disease.”