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New DNA test beats others at hunting down germs that inflame the brain, study finds

Cathie Anderson, The Sacramento Bee on

Published in Science & Technology News

Right now, neurologists don't have one test that can identify multiple causes of inflammatory neurological diseases such as encephalitis and meningitis. But UC San Francisco researchers say their new DNA test hunted down more of these pathogens than any conventional test did in a newly released study.

Inflammatory neurological diseases are rare, costly to treat, difficult to diagnose and life-threatening.

The pioneering test developed by neurological researchers at UCSF is moving doctors closer to providing patients and their loved ones with the answers they seek. The test uses gene sequencing to identify more causes of these mysterious ailments than any conventional test now being used, according to study released late last week in the New England Journal of Medicine.

Conventional test look for pathogens one at a time, so that means physicians essentially have to know what they're looking for to choose the right test to perform, UCSF researchers said. Without knowing the cause of these ailments, they said, it's impossible to know what treatments to employ.

"Patients with infectious and noninfectious encephalitis can be clinically indistinguishable from one another," said Dr. Michael Wilson, associate professor of neurology at UCSF and the co-first author of the paper, along with study coordinator Hannah Sample. "Having a broad-based test that either rules in infection or rules out infection can really aid these cases that are in gray areas between infection and not."

Infections cause less than half of most meningitis and encephalitis cases, UCSF researchers said. The rest result mostly from autoimmune system reactions.

 

The last thing doctors want to do is suppress the immune system of a patient with an infection because the consequences could be harmful, Wilson and other researchers explained. Yet that's precisely what is needed for a patient with an autoimmune disease.

To prevent delays and errors, Wilson, Dr. Charles Chiu and other UCSF researchers came up with a test they call mNGS, short for metagenomic next-generation sequencing. It identifies the pathogens found in a patient's cerebrospinal fluid by sequencing the genes of invading viruses, fungi, bacteria or other organisms.

Chiu said their team was "frankly surprised" to discover that a significant proportion of the diagnosed infections -- 13 of 58, or 22.4% -- were detected only by the mNGS test, despite exhaustive and comprehensive testing done in hospitals offering highly specialized neurological care.

"This highlighted the usefulness, and perhaps the necessity, of introducing new diagnostic technologies into the clinic to enable more timely and accurate diagnoses that will hopefully lower health care costs, decrease lengths of stay, and ultimately save lives," said Chiu, also director of the UCSF-Abbott Viral Diagnostics and Discovery Center.

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