Targeted Liquid Chromatography-Mass Spectrometry-Based Laboratory Developed Tests (LDTs) for Alzheimer's Disease Protein Biomarkers Research

Alzheimer’s disease (AD) is the most common form of dementia, with cerebrospinal fluid (CSF) beta-amyloid and tau providing the most sensitive and specific biomarkers for diagnosis. However, these diagnostic biomarkers do not reflect the heterogenous and complex changes in AD brain. We have demonstrated the ability to use targeted LC/MS to quantify additional CSF proteins at different stages of AD.

We injected 20µL of the same digested CSF samples using nearly equivalent LC/MS method parameters on the 6495C LC/TQ and Ultivo LC/TQ to compare detection limits, reproducibility, and disease specificity. Detection limits were estimated using quantitative isotopically labeled peptide standards. Reproducibility was assessed using pool CSF quality controls (QC). Disease specificity was determined by comparing the LC/MS data to the immunoassay data.

In our preliminary data with 192 CSF samples including 16 QCs, we found 27 peptides with coefficient of variation (CV) <=30% and R-squared >=0.8 from linear regression indicating a high degree of reproducibility and correlation between both LC/MS systems. Ten peptides showed moderate correlation with R-squared values between 0.6-0.8 and require further investigation to determine possible interfering or alternate transitions.

Presenter:  Dr. Caroline Watson (Associate Scientist, Department of Neurology, Emory University School of Medicine)