The Relationship between Different Assays for Detection and Quantification of Amyloid Beta 42 in Human Cerebrospinal Fluid

Alzheimer's disease (AD), which is characterized by a degeneration of neurons and their synapses, is one of the most common forms of dementia. CSF levels of amyloid β (42) (Aβ (42)) have been recognized as a strong candidate to serve as an AD biomarker. There are a number of commercial assays that are routinely employed for measuring Aβ (42); however, these assays give diverse ranges for the absolute levels of CSF Aβ (42). In order to employ CSF Aβ (42) as a biomarker across multiple laboratories, studies need to be performed to understand the relationship between the different platforms. We have analyzed CSF samples from both diseased and nondiseased subjects with two different widely used assay platforms. The results showed that different values for the levels of CSF Aβ (42) were reported, depending on the assay used. Nonetheless, both assays clearly demonstrated statistically significant differences in the levels of Aβ (42) in CSF from AD relative to age-matched controls (AMC). This paper provides essential data for establishing the relationship between these assays and provides an important step towards the validation of Aβ (42) as a biomarker for AD.