Janelidze S, Teunissen CE, Zetterberg H, et al. - The results of 2 independent cohorts show that certain mass spectrometry (MS)-based methods outperformed most immunoassays for plasma amyloid-β 42/40 (Aβ42/40) when identifying brain Aβ pathology.

• In total, 408 candidates were involved in this research.

• The mean (SD) age of the BioFINDER cohort was 71.6 (5.6) years, and 49.3% of the cohort were female.

• When it came to detecting persons with aberrant CSF Aβ42/40 in the whole cohort, plasma IP-MS-WashU Aβ42/40 outperformed LC-MS-Arc Aβ42/40, IA-Elc Aβ42/40, IA-EI Aβ42/40, and IA-N4PE Aβ42/40.

• In the 2 subcohorts where these biomarkers were available, plasma IP-MS-WashU Aβ42/40 performed significantly better than IP-MS-UGOT Aβ42/40 and IA-Quan Aβ42/40, but there was no difference in AUCs between IP-MS-WashU Aβ42/40 and IP-MS-Shim Aβ42/40.

• When Aβ-PET was used as the outcome, the results were comparable.

• The strongest coefficients for correlations with CSF Aβ42/40 were seen in plasma IPMS-WashU Aβ42/40 and IPMS-Shim Aβ42/40.

• The BioFINDER findings were replicated in the Alzheimer Disease Neuroimaging Initiative cohort (mean [SD] age, 72.4 [5.4] years; 43.4% women), where the IP-MS-WashU assay outperformed the IP-MS-UGOT, IA-Elc, IA-N4PE, and IA-Quan assays but not the IP-MS-Shim assay.