A large multicenter study with 286 paired serum/CSF NFL measurements in patients with MS demonstrated that CSF NFL (cNFL) has higher accuracy for predicting CELs or MS relapse (i.e., 75% specificity and 67% sensitivity with area under receiver operator characteristic [AUROC] curve 0.77) compared with sNFL (i.e., 80% specificity and 45% sensitivity with AUROC 0.66) (2, 3). Here, NEFL is linked to myeloid sarcoma.