Comparing Biomarker Platforms
The Alzheimer’s Disease Research Centers (ADRC) Program has, and continues to, shape the future of Alzheimer’s disease (AD) research. Part of what makes the Program especially impactful is its use of standardized data collection methods across all Centers.
Yet, recent research from the University of Washington ADRC raises concerns that consistent sample and clinical data collection may not be sufficient when it comes to understanding biomarker findings derived from plasma and CSF samples.
Cameron Afzal, MD Candidate at Tufts University School of Medicine, spent this summer working with the UW ADRC to research discrepancies in results from analyses of plasma and CSF biomarkers samples run on different research instruments.
Before starting medical school, Afzal had worked as a research coordinator at the UW ADRC. Looking for a summer research project that could connect his various interests, he reached out to the UW ADRC and learned about a fluid biomarker validation project awaiting further analysis.
Nearly 200 plasma samples were collected in 2023 and 2024 from research participants at the UW ADRC. In collaboration with the National Centralized Repository for Alzheimer’s Disease and Related Dementias (NCRAD) the samples were analyzed as part of a pilot validation project of plasma samples run on different platforms.
The samples analyzed included plasma pTau-181 samples measured using the SR-X Quanterix analyzer at the UW ADRC and using the HD-X Quanterix analyzer at NCRAD. CSF Aβ42, Aβ42/Aβ40, tTau, pTau-181, and pTau-181/Aβ42 were measured using different platforms: using AlzBio, Lumipulse, or Millipore assays analyzed on the Luminex 200 instrument at the UW ADRC.
The study found that although the samples were collected from the same participants at the same time, they had statistically significant differences in the analyzed results across platforms. For example, the NCRAD-analyzed results were found to be consistently higher than those analyzed at the UW ADRC, even though the results were significantly correlated.
In his research, Afzal found that though the results were different between methods of analysis, there were consistencies across samples of both plasma and CSF. “The results were proportional within each kit, like in the plasma, the same patients are going to be in the top third, middle third, and bottom third of how high or low their p-tau181 is. This indicates that the kit itself is not necessarily giving inaccurate results, but they’re all skewed up or skewed down,” Afzal said.
“...the kit itself is not necessarily giving inaccurate results, but they’re all skewed up or skewed down.”
Though this initial research raises concerns about the impact of using different kits to analyze biomarkers, the sample size available for this research was not sufficient to make further conclusions regarding how these results might correlate with clinical diagnoses such as MCI or Alzheimer’s disease. “Unfortunately, we don’t have samples on enough participants to get statistically significant results for that. If we tried to do comparisons between the participants who had both [blood and CSF samples] or between disease states, we would have categories with only one participant in them,” Afzal said.
“We initially tried deriving cut points in each kit to determine what is a positive or negative result for testing for Alzheimer’s [in these kits], and, unfortunately again, the problem was we don’t have the sample size in order to actually do that.”
Investigators globally and within the ADRC Program are aware of the differences between biomarker platforms and are focusing on ways to harmonize biomarker data collection for the purpose of understanding ways to best standardize biomarker interpretation. While more research is needed into the validation of fluid biomarkers run on different platforms and the potential impact on disease diagnosis, these findings may be especially relevant across the ADRC Program where biomarkers are consistently analyzed both locally and at NCRAD.
Any ADRC members interested in learning more about this study or in collaborating on future related research are encouraged to reach out to Lynn Bekris, lead of the UW ADRC fluid biomarker core.