Lower baseline cerebrospinal fluid amyloid-β 42 is associated with amyloid-related imaging abnormalities during real-world lecanemab treatment

Amyloid-related imaging abnormalities (ARIA) are a safety concern during lecanemab treatment for early Alzheimer's disease. We examined baseline cerebrospinal fluid amyloid-β 42 (Aβ 42 ) in 97 lecanemab-treated patients; 11 developed ARIA. Aβ 42 was lower in ARIA cases than in non-ARIA cases (483.2 ± 108.6 versus 667.4 ± 185.4 pg/mL; p < 0.001). ROC analysis yielded an AUC of 0.806 (95% CI, 0.670–0.919). Aβ 40 was also lower, whereas the Aβ 42 /Aβ 40 ratio was not significantly different and tau biomarkers were not higher. Lower Aβ 42 was associated with subsequent ARIA, but the internally derived cutoff requires external validation.