Biomarkers in Spinal Fluid Offer Method for Alzheimer's Diagnosis

September 27, 2018
By Allen Cone

Researchers have developed a spinal fluid test that can accurately identify most patients with Alzheimer's disease, according to a clinical study.

By tapping amyloid and tau levels in cerebrospinal fluid, Columbia University neurologists may have found a reliable way to help diagnose the disease. The findings were published this week in the Journal of Alzheimer's Disease.

Currently, no single test can definitively identify Alzheimer's, a neurological disease where dementia symptoms gradually worsen over a number of years.

"Our study shows that this is a good test that can be used in clinical practice to reliably exclude other diagnoses in patients suspected of having Alzheimer's disease," Dr. Richard Mayeux, chairman of the Department of Neurology at Columbia University Vagelos College of Physicians and Surgeons, said in a press release. "It's better than amyloid PET scans, which only look at the amount of amyloid protein in the brain, because it measures amyloid and two types of tau protein."

Cerebrospinal fluid can determine the brain's condition because of its direct contact with the brain.

Certain levels of tau and amyloid proteins in this fluid have been found to be associated with the disease.

While neurologists have included tests for the two biomarkers when doing diagnostic workups of cerebrospinal fluid, a previous analysisof 231 studies suggested the test has limited benefits in clinical practice.

"But these studies only compared individuals who had been clinically diagnosed with Alzheimer's with healthy controls," Mayeux said. "That doesn't reflect what's done in clinical practice, where physicians must determine whether dementia and other symptoms are due to Alzheimer's or other diseases."

For the new study, researchers examined data from 1,016 patients at Columbia University Irving Medical Center with various forms of dementia or mild cognitive impairment. The patients had undergone lumbar puncture between 2005 and 2017, and the cerebrospinal fluid samples were sent to a commercial laboratory for analysis.

The test identified roughly 90 percent of those with a clinical diagnosis of Alzheimer's disease, compared with patients with no dementia or other types of dementia. Also, the test correctly identified about 70 percent to 80 percent of patients with other types of dementia or mild cognitive impairment, but didn't distinguish among the different types.

"Our study shows that this is a good test, just missing the accuracy in distinguishing between Alzheimer's and non-Alzheimer's dementia or mild cognitive impairment needed to make it an excellent test," Mayeux said.

In the 30- to 40-minute procedure, a lumbar puncture is performed with a local anesthetic to collect the fluid. The authors noted fewer than 5 percent of patients experienced a headache after this procedure.

The test costs around $1,000 -- compared with $3,500 for an amyloid PET scan -- and "is much easier to administer and is much safer than many people think," Mayeux said.

Researchers plan to perform additional studies to determine if other proteins in cerebrospinal fluid can improve the test's ability to distinguish Alzheimer's from other dementias. [read more]