NEFL and X-linked adrenoleukodystrophy: In this study, we used logistic regression analysis and blood samples from a discovery cohort of childhood CALD and asymptomatic X-ALD patients to determine a plasma NfL cut-off value of 8.33 pg/mL to differentiate CALD-indicative cerebral lesions with a sensitivity of 100% and a specificity of 95.2% in childhood/adolescent X-ALD patients (4–18 years).