new research suggests.
In a study of more than 1,000 participants, changes over time in levels of p-tau181 were associated with prospective neurodegeneration and cognitive decline characteristic of Alzheimer’s disease. These results have implications for investigative trials as well as clinical practice, the investigators noted.
Like p-tau181, neurofilament light chain (NfL) is associated with imaging markers of degeneration and cognitive decline; in contrast to the findings related to p-tau181, however, the associations between NfL and these outcomes are not specific to Alzheimer’s disease. Using both biomarkers could improve prediction of outcomes and patient monitoring, according to the researchers.
“These findings demonstrate that p-tau181 and NfL in blood have individual and complementary potential roles in the diagnosis and the monitoring of neurodegenerative disease,” said coinvestigator Michael Schöll, PhD, senior lecturer in psychiatry and neurochemistry at the University of Gothenburg (Sweden).
“With the reservation that we did not assess domain-specific cognitive impairment, p-tau181 was also more strongly associated with cognitive decline than was NfL,” Dr. Schöll added.
The findings were published online Jan. 11 in JAMA Neurology.
Biomarker-tracked neurodegeneration
Monitoring a patient’s neurodegenerative changes is important for tracking Alzheimer’s disease progression. Although clinicians can detect amyloid-beta and tau pathology using PET and cerebrospinal fluid (CSF) biomarkers, the widespread use of the latter has been hampered by cost and limited availability of necessary equipment. The use of blood-based biomarkers is not limited in these ways, and so they could aid in diagnosis and patient monitoring.
Previous studies have suggested that p-tau181 is a marker of Alzheimer’s disease status.
In the current study, investigators examined whether baseline and longitudinal levels of p-tau181 in plasma were associated with progressive neurodegeneration related to the disease. They analyzed data from the Alzheimer’s Disease Neuroimaging Initiative, a multicenter study designed to identify biomarkers for the detection and tracking of Alzheimer’s disease.
The researchers selected data for cognitively unimpaired and cognitively impaired participants who participated in the initiative between Feb. 1, 2007, and June 6, 2016. Participants were eligible for inclusion if plasma p-tau181 and NfL data were available for them and if they had undergone at least one 18fluorodeoxyglucose (FDG)–PET scan or structural T1 MRI at the same study visit. Most had also undergone imaging with 18florbetapir, which detects amyloid-beta.
A single-molecule array was used to analyze concentrations of p-tau181 and NfL in participants’ blood samples. Outliers for p-tau181 and NfL concentrations were excluded from further analysis. Using participants’ FDG-PET scans, the investigators measured glucose hypometabolism characteristic of Alzheimer’s disease. They used T1-weighted MRI scans to measure gray-matter volume.
Cognitively unimpaired participants responded to the Preclinical Alzheimer Cognitive Composite, a measure designed to detect early cognitive changes in cognitively normal patients with Alzheimer’s disease pathology. Cognitively impaired participants underwent the Alzheimer Disease Assessment Scale–Cognitive Subscale with 13 tasks to assess the severity of cognitive impairment.
The researchers included 1,113 participants (54% men; 89% non-Hispanic Whites; mean age, 74 years) in their analysis. In all, 378 participants were cognitively unimpaired, and 735 were cognitively impaired. Of the latter group, 73% had mild cognitive impairment, and 27% had Alzheimer’s disease dementia.