Clinical validation of the Lumipulse G cerebrospinal fluid assays for routine diagnosis of Alzheimer’s disease

Abstract

BackgroundOngoing efforts within the Alzheimer’s disease (AD) field have focused on improving the intra- and inter-laboratory variability for cerebrospinal fluid (CSF) biomarkers. Fully automated assays offer the possibility to eliminate sample manipulation steps and are expected to contribute to this improvement. Recently, fully automated chemiluminescence enzyme immunoassays for the quantification of all four AD biomarkers in CSF became available. The aims of this study were to (i) evaluate the analytical performance of the Lumipulse G β-Amyloid 1-42 (restandardized to Certified Reference Materials), β-Amyloid 1-40, total Tau, and pTau 181 assays on the fully automated LUMIPULSE G600II; (ii) compare CSF biomarker results of the Lumipulse G assays with the established manual ELISA assays (INNOTEST®) from the same company (Fujirebio); and (iii) establish cut-off values and the clinical performance of the Lumipulse G assays for AD diagnosis.MethodsIntra- and inter-assay variation was assessed in CSF samples with low, medium, and high concentrations of each parameter. Method comparison and clinical evaluation were performed on 40 neurological controls (NC) and 80 patients with a diagnosis of probable AD supported by a follow-up ≥ 3 years and/or positive amyloid PET imaging. A small validation cohort of 10 NC and 20 AD patients was also included to validate the cut-off values obtained on the training cohort.ResultsThe maximal observed intra-assay and inter-assay coefficients of variation (CVs) were 3.25% and 5.50%, respectively. Method comparisons revealed correlation coefficients ranging from 0.89 (for Aβ40) to 0.98 (for t-Tau), with those for Aβ42 (0.93) and p-Tau (0.94) in-between. ROC curve analysis showed area under the curve values consistently above 0.85 for individual biomarkers other than Aβ40, and with the Aβ42/40, Aβ42/t-Tau, and Aβ42/p-Tau ratios outperforming Aβ42. Validation of the cut-off values in the independent cohort showed a sensitivity ranging from 75 to 95% and a specificity of 100%. The overall percentage of agreement between Lumipulse and INNOTEST was very high (> 87.5%).ConclusionsThe Lumipulse G assays show a very good analytical performance that makes them well-suited for CSF clinical routine measurements. The good clinical concordance between the Lumipulse G and INNOTEST assays facilitates the implementation of the new method in routine practice.

Alzheimer’s Cerebrospinal Biomarkers from Lumipulse Fully Automated Immunoassay: Concordance with Amyloid-Beta PET and Manual Immunoassay in Koreans

“…The excellent analytical performance for the assays has been described previously. [21][22][23] Amyloid Positron Emission Tomography 271 subjects out of 331 participants underwent amyloid imaging via 11 C-PiB PET or 18 F-utemetamol PET. We aligned PET images to the corresponding T 1 -weighted MRI and the standard uptake value ratio (SUVR) of each region of interest (ROI), which was obtained by dividing the mean uptake value for all voxels within the ROI by the mean value of the reference region.…”

Measurement of CSF core Alzheimer Disease biomarkers for routine clinical diagnosis: do fresh vs frozen samples differ?

“…The standardization of preanalytical and analytical procedures (i.e., freeze/thaw cycles [11], CSF storage volumes [11], pipettetips and tube materials [12,13], storage temperature [14] and variability due to the operator [15]) represents a crucial factor in biomarker assays [10]. In this context, automated [16][17][18][19][20] and semiautomated [21] platforms may play a major role in minimizing inter-laboratory differences in biomarker assays. Fully automated chemiluminescent platforms [20], showed high sensitivity and specificity for early diagnosis of AD, with an optimal concordance with manual ELISA assays [18,20] and amyloid-targeted Positron Emission Tomography (PET) [19,22].…”

“…In this context, automated [16][17][18][19][20] and semiautomated [21] platforms may play a major role in minimizing inter-laboratory differences in biomarker assays. Fully automated chemiluminescent platforms [20], showed high sensitivity and specificity for early diagnosis of AD, with an optimal concordance with manual ELISA assays [18,20] and amyloid-targeted Positron Emission Tomography (PET) [19,22]. Moreover, these platforms offer the possibility to easily and quickly analyze any single and fresh CSF samples, a feature that could be useful when a timely response is needed by clinicians.…”

Measurement of CSF core Alzheimer Disease biomarkers for routine clinical diagnosis: do fresh vs frozen samples differ?

“…The standardization of pre-analytical and analytical procedures (i.e., freeze/thaw cycles [11], CSF storage volumes [11], pipette-tips and tube materials [12,13], storage temperature [14] and variability due to the operator [15]) represents a crucial factor in biomarker assays [10]. In this context, automated [16][17][18][19][20] and semi-automated [21] platforms may play a major role in minimizing inter-laboratory differences in biomarker assays. Fully automated chemiluminescent platforms [20], showed high sensitivity and speci city for early diagnosis of AD, with an optimal concordance with manual ELISA assays [18,20] and amyloid-targeted Positron Emission Tomography (PET) [19,22].…”

“…In this context, automated [16][17][18][19][20] and semi-automated [21] platforms may play a major role in minimizing inter-laboratory differences in biomarker assays. Fully automated chemiluminescent platforms [20], showed high sensitivity and speci city for early diagnosis of AD, with an optimal concordance with manual ELISA assays [18,20] and amyloid-targeted Positron Emission Tomography (PET) [19,22].…”