A test that measures changes in a patients’ blood protein levels through blood samples, brain imaging and cognitive tests could detect Alzheimer's disease up to 16 years before symptoms appear, according to new research published online in Nature Medicine.
By measuring changes in the levels of a protein in the blood called neurofilament light chain (NfL), researchers led by Mathias Jucker, PhD, a professor of cell biology of neurological diseases at the German Center for Neurodegenerative Diseases in Tübingen, Germany, believe heightened levels of the protein could be an early indicator of the disease.
NfL is a biomarker in the blood which indicates nerve cell loss in the brain. Increasing levels of NfL mean more brain damage to the patient, which often precedes the symptoms of Alzheimer’s. As of 2014, roughly five million Americans were diagnosed with Alzheimer’s disease, according to the U.S. Centers for Disease Control and Prevention.
Although no effective treatments for Alzheimer’s currently exist, Jucker and colleagues hope their test could help monitor the effectiveness of new treatments and how levels of NfL are affected before patients start to experience symptoms of the disease.
For their study, the team measured the rate of change in NfL in 405 patients from around the world enrolled in the Dominantly Inherited Alzheimer’s Network (DIAN). The network evaluates a rare form of Alzheimer's developed by those who inherit a gene mutation that predisposes them to the disease.
NfL protein samples were measured in the patients through blood samples from cerebrospinal fluid (CSF) and serum, brain imaging (18F-fluorodeoxyglucose (18F-FDG) PET) and cognitive tests once every two and a half years over the last seven years. The researchers noted the study is ongoing.
A group of 243 patients carrying a gene mutation which increased their risk of Alzheimer's disease had increasing levels of NfL more than six years before symptoms began, compared to 162 family members without the mutation who did not show increasing levels of NfL.
Of the 243 patients with the gene mutation and increasing levels of NfL, 13 of them eventually developed Alzheimer's. The researchers also found a correlation between increasing NfL levels, cognitive decline and loss of brain volume.
“In presymptomatic Alzheimer’s disease, the greater the NfL rate of change, the closer an individual is to converting to symptomatic Alzheimer’s disease, a finding also reported for cortical atrophy,” Jucker et al. concluded. “This suggests that longitudinal measures of NfL in the serum are a reliable, relatively cheap, and fast readout of neurodegeneration in the brain with comparable diagnostic value to neuroimaging but without the regional resolution.”