Parkinson's disease diagnosis could be aided with blood test

Swedish researchers say a simple blood test is effective at differentiating symptoms of Parkinson's disease from similar disorders, but it isn't ready for clinical use.

In its early stages, neurologists say Parkinson's is difficult to distinguish from rarer disorders, called atypical parkinsonian disorders. They have overlapping symptoms that tend to worsen more quickly and are more likely to lead to death.

Researchers are on the hunt for biomarkers to help diagnosis these disorders. One potential biomarker, a nerve protein that can be detected when nerve cells die, is found in higher concentrations in spinal fluid collected by lumbar puncture. Now medical scientists have also found the protein in less invasive blood tests.

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For the study published in Wednesday's online issue of the journal Neurology, Dr. Oskar Hansson of Sweden's Lund University and his team examined 504 people in three groups.

Two of the groups, in England and Sweden, included healthy people and those who had been living with one of the disorders for an average of four to six years. The third group of 109 patients had the diseases for three years or less.

"The results of the present study strongly indicate that NfL when measured in blood can be used to distinguish between patients with Parkinson's disease and patients with progressive supranuclear palsy multiple system atrophy and corticobasal degeneration with high diagnostic accuracy," the study's authors said.

Hansson said concentrations of the nerve protein could discriminate between the diseases as accurately as its concentrations in spinal fluid.

Blood biomarkers have previously been considered in diagnosing Alzheimer disease but other teams weren't able to reproduce those findings.

That's why the Hansson's team turned to people at clinics in different countries in their evaluation.

Not there yet

The results also seem highly reliable, Dr. Guido Alves of the neurology department at Stavanger University Hospital in Norway and his co-author said in a journal editorial.

While NfL levels help distinguish Parkinson's from the other disorders, it can't separate the other three, which would help clinicians, Alves said.

Most patients with Parkinson's showed NfL levels in the normal range. "We still lack an easily accessible disease-specific diagnostic biomarker for the most common movement disorder," according to the editorial.

The test was a research tool. To use it clinically, several more steps are needed. For instance, scientists need to determine cutoff values to flag abnormal levels.

But the value of early diagnosis is less clear when few disease-modifying treatments exist.

The study was supported by the European Research Council, the Swedish Research Council, The Parkinson Foundation of Sweden, the Swedish Brain Foundation, the Knut and Alice Wallenberg Foundation, the Torsten Soderberg Foundation at the Royal Swedish Academy of Sciences and the Swedish Federal Government under the ALF Agreement.