Analytical and clinical performances of the automated Lumipulse cerebrospinal fluid Aβ42 and T-Tau assays for Alzheimer's disease diagnosis.

BACKGROUND: Cerebrospinal fluid (CSF) biomarkers are increasingly used to diagnose Alzheimer's disease (AD). However, important methodological and technical remain regarding measurement variability between kit providers and users. We compared the Lumipulse fully automated assays with the manual INNOTEST assays (both from Fujirebio Europe NV, Gent, Belgium) on a clinically representative sample of patients and controls.
METHODS: CSF samples of 156 patients were used to quantify Amyloïd Aβ1-42 peptide (Aβ1-42) and Total-Tau (T-Tau) protein by chemiluminescent enzyme-immunoassay (Lumipulse). Patients were divided into several subgroups: Alzheimer (AD = 44), mild-cognitive impairment (MCI = 23), other dementias (OD = 36), non-dementing neurological conditions (ND = 11), and controls (CTRL = 42). Clinical cut-offs were determined by comparing AD and CTRL with ROC curves for the two markers and their related ratio (T-Tau/Aβ1-42). Subgroups of 58 (for phosphorylated-Tau) and 115 samples (for Aβ1-42 and T-Tau) were used to evaluate the concordance of this analyzer with the INNOTEST assays.
RESULTS: Lumipulse and INNOTEST assays showed good concordance for all markers, but systematic bias was observed justifying the need to redefine new clinical cut-offs. To discriminate AD from CTRL subjects, T-Tau/Aβ1-42 ratio was the best biomarker, with a cut-off value of 1.12 (sensitivity 81.8% and specificity 92.9%). Similar clinical performances were observed for the Lumipulse and Innotests assays on the subsample of 115 subjects.
CONCLUSIONS: Our results demonstrate that the Lumipulse Aβ1-42 and T-Tau assays show good analytical and clinical performances in the context of patient evaluation referred to a memory clinic. Automated analyzers should be preferred for the measurement of CSF AD biomarkers to reduce inter- and intra-laboratory variability.