Round robin test on quantification of amyloid-β 1-42 in cerebrospinal fluid by mass spectrometry.

Introduction: Cerebrospinal fluid (CSF) amyloid-β 1-42 (Aβ42) is an important biomarker for Alzheimer's disease, both in diagnostics and to monitor disease-modifying therapies. However, there is a great need for standardization of methods used for quantification. To overcome problems associated with immunoassays, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a critical orthogonal alternative.

Methods: We compared results for CSF Aβ42 quantification in a round robin study performed in four laboratories using similar sample preparation methods and LC-MS instrumentation.

Results: The LC-MS results showed excellent correlation between laboratories (r(2) >0.98), high analytical precision, and good correlation with enzyme-linked immunosorbent assay (r(2) >0.85). The use of a common reference sample further decreased interlaboratory variation.

Discussion: Our results indicate that LC-MS is suitable for absolute quantification of Aβ42 in CSF and highlight the importance of developing a certified reference material.