B-083 Validation of Alzheimer’s Disease Markers in CSF

Background Alzheimer*s Disease (AD) is a progressive neurodegenerative disorder that leads to cognitive decline and memory loss. It is characterized by the accumulation of ß-amyloid plaques and neurofibrillary tangles composed of tau protein in the brain. Early and accurate diagnosis of AD is crucial for patient management and therapeutic intervention. Biomarkers in cerebrospinal fluid (CSF), including ß-amyloid (1-42) (Abeta42), phospho-tau (p-Tau 181), and total-Tau (tTau), are an important aid in the diagnosis of AD. The aim of this study was to evaluate the analytical performance of these biomarkers using the Roche cobas pro e801 platform in a clinical laboratory setting. Methods Accuracy, linearity, precision, and sensitivity of the ß-amyloid (1-42) CSF II, Phospho-Tau (181P CSF), and Total-Tau CSF assays were determined according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Additional studies assessed assay specificity and stability of the analytes. Residual patient specimens were used to assess accuracy, specificity, and stability. Manufacturer linearity and quality control materials were used to assess linearity, precision and sensitivity. Results Method comparisons against an external lab employing the same methodology, revealed strong agreement with the following results from Deming regression analysis [assay (slope, % bias, R)]: ß-amyloid (1-42) (1.009, -1.3%, 0.988), 181P (0.979, -5.6%, 0.989), Total-Tau (0.975, -2.4%, 0.985). Linearity for all three assays was confirmed, with recoveries ranging from 94% to 107% across the manufacturer’s analytical measurement range. The maximum observed within-run, between-run, and total-assay coefficients of variation (CVs) were 1.2%, 0%, and 1.4%, respectively. The limit of detection was verified (100 pg/mL (ß-amyloid (1-42) CSF II), 8 pg/mL (181P CSF), and 80 pg/mL (Total-Tau CSF)). For ß-amyloid (1-42) CSF II, hemolysis interference was observed at hemoglobin levels above 100 mg/dL, resulting in greater than 10% decrease from the initial value, while quantification of p-Tau 181 and tTau were not affected by hemoglobin up to the 250 mg/dL tested. Sample stability assessments confirmed that Abeta42, p-Tau 181, and tTau are stable for up to 5 days at ambient temperature, 14 days refrigerated, and 8 weeks frozen, with no more than one freeze/thaw cycle allowed. Simulated transportation did not impact analyte concentration when samples were refrigerated, confirming the suitability of refrigerated shipping. Conclusion The Roche cobas pro ß-amyloid (1-42) CSF II, Phospho-Tau (181P CSF), and Total-Tau CSF assays exhibited excellent precision and linearity across the analytical measurement range. The assay accurately quantified protein concentrations when compared to another laboratory running the Roche assays. Overall, the validated assays provide a reliable means for measuring Abeta42, p-Tau181, and tTau concentrations in CSF on a Roche chemistry analyzer, aiding in early diagnosis of AD.