Diagnostic performance of plasma p-tau217 levels measured with different assays for Alzheimer’s disease

Plasma tau phosphorylated at threonine 217 (p-tau217) has been recommended as a biomarker for the diagnosis of Alzheimer's disease (AD). We evaluated the diagnostic and differential performance of plasma p-tau217 levels measured with three novel assays in a Chinese population. A total of 233 participants were recruited, including 39 cognitively unimpaired controls (CUCs), 28 individuals with mild cognitive impairment (MCI) due to AD, 57 individuals with AD dementia (ADD), 70 individuals with subcortical ischemic vascular dementia (SIVD), and 39 individuals with frontotemporal lobar degeneration (FTLD). Plasma p-tau217 levels were measured using one assay based on single-molecule techniques (DiSMS), one assay based on digital ELISA (LyMedivh™ AXL), and one assay based on flow cytometry (CBA), as well as a reference assay (ALZpath Simoa). Group differences in plasma p-tau217 levels were assessed using analysis of covariance, and the diagnostic and differential performance of the assays was evaluated via receiver operating characteristic analysis. Partial correlation analysis was used to examine the correlations between the measurements of the three novel assays and those of the reference assay. We found that plasma p-tau217 levels measured with all three novel assays were higher in the ADD group than in the CUC, SIVD, and FTLD groups (all p < 0.05) and effectively discriminated ADD patients from both CUCs and non-AD dementia patients. The diagnostic and differential performances did not significantly differ among the three assays (all p > 0.05). Both the DiSMS and LyMedivh™ AXL assays also revealed elevated plasma p-tau217 levels in the MCI group compared to the CUC group. Moreover, the measurements of the three novel assays demonstrated significant correlations with the ALZpath Simoa measurements (p < 0.01). When using their optimal cutoff values, both the DiSMS and LyMedivh™ AXL assays yielded a specificity of 100% and a sensitivity of 94.4%, and the CBA assay showed a specificity of 100% and a sensitivity of 88.9%. In conclusion, our study demonstrated the diagnostic and differential abilities of plasma p-tau 217 levels measured with three novel assays that can serve as potential alternatives to the currently available testing methods for AD diagnosis.