Performance of optimized prototype LUMIPULSE G immunoassays for plasma pTau181 and pTau217

Abstract

AbstractBackgroundThere is a need for automated random access plasma phosphorylated Tau (pTau) methods that reflect AD pathology with consistent performance. LUMIPULSE (LP) assays could offer a solution. Initial prototype pTau181 and pTau217 LP assays showed lower clinical performance versus Quanterix Homebrew assays (Poster #79533 – P4‐06). This new study presents optimized pTau181 and pTau217 LP assays, showing data on their analytical and clinical performance compared to the initial prototype method (Ref) and an in‐house pTau181 Quanterix Homebrew assay.MethodPlasma pTau181 and pTau217 LP assays were developed using recombinant pTau181 mAb RD‐070, resp. pTau217 mAb RD‐085, combined with an ALP‐Fab conjugate from recombinant N‐terminal Tau mAb RD‐073. In the optimized automated protocol, an assay specific diluent (ASD) is added (20%) to the sample to increase signal specificity. Analytical and clinical performance of the reference versus ASD‐treated prototypes to distinguish AD from controls was evaluated using 40 CSF‐confirmed AD‐dementia and 40 age‐matched healthy volunteer plasma samples.ResultAnalytical performance: Both optimized pTau181 and pTau217 LP tests demonstrated high precision comparable to their reference assays (inter‐run %CV on 3 neat plasma samples < 7.4). LLOQ was not affected by ASD‐treatment. Clinical performance: pTau181 LP assays demonstrated comparable AUC and median fold change with (AUC 0.828, fold change 1.9) and without ASD (AUC 0.823, fold change 1.5) while the SIMOA assay demonstrated a higher AUC (0.866) and fold change (2.9). For pTau217, the performance improved from an initial AUC of 0.918 to 0.935, and a fold change of 3.72 instead of initially 2.76. (Figure 1). All assays correlated strongly (p<0.00001) (Table 1); highest correlations among them were observed with the pTau217 ASD‐treated assay.ConclusionUsing an assay specific diluent resulted in improved clinical performance for the pTau217 prototype LUMIPULSE assay, in line with other published pTau217 assays. We did not achieve improved performance of the pTau181 LP assay with the ASD addition. Most important to emphasize, a performant pTau217 assay prototype is under development on an fully automated, scalable platform. Next steps include verification of performance in additional well‐characterized AD cohorts and characterization of lot consistency and robustness of the pTau181 and pTau217 N‐terminal LUMIPULSE assays.