Taking the A Train? Limited Consistency of Aβ42 and the Aβ42/40 Ratio in the AT(N) Classification

The consistency of cerebrospinal fluid amyloid-beta (A beta(42/40) ratio and A beta(42) has not been assessed in the AT(N) classification system. We analyzed the classification changes of the dichotomized amyloid status (A+/A-) in 363 patients tested for Alzheimer's disease biomarkers after A beta(42) was superseded by the A beta(42/40) ratio. The consistency of A beta(42) and the A beta(42/40) ratio was very low. Notably, the proportions of false A+T- patients were considerable (74-91%) and corresponded mostly to patients not clinically diagnosed with Alzheimer's disease. Our results suggest that the interchangeability of A beta(42/40) ratio and A beta(42) is limited for classifying patients in clinical setting using the AT(N) scheme.

Automated summary

The consistency between cerebrospinal fluid amyloid-beta (A beta(42/40) ratio and A beta(42) in the AT(N) classification system is limited. Most false A+T- patients were not clinically diagnosed with Alzheimer's disease. Therefore, the interchangeability of A beta(42/40) ratio and A beta(42) is restricted in classifying patients in a clinical setting using the AT(N) scheme.