Integrating Serum Neurofilament Light Chain Into Amyotrophic Lateral Sclerosis Diagnostic Criteria

INTRODUCTION/AIMS: Serum neurofilament light chain (NfL) is a promising diagnostic biomarker for differentiating amyotrophic lateral sclerosis (ALS) from clinical mimics. This study assessed the utility of integrating serum NfL into current diagnostic criteria to enhance diagnostic certainty in patients with a provisional ALS diagnosis who were confirmed as having ALS at follow-up. METHODS: We conducted a single-center, retrospective study of consecutive patients with a provisional ALS diagnosis at their initial visit at the WashU Medicine ALS Center. All underwent electrodiagnostic testing and serum NfL measurement via SIMOA using an HD-X analyzer (Quanterix). Elevated serum NfL was defined with a cutoff of 38 pg/mL. RESULTS: The study included 43 patients with a provisional ALS diagnosis (29 men [67.4%]; median age, 63 years [range, 36-80 years]). At follow-up, 27/43 (62.8%) patients progressed to definite ALS. Serum NfL was elevated in 34/43 (79.1%) of the total cohort and 24/27 (88.9%) of those who progressed to definite ALS. Integrating serum NfL with Gold Coast Criteria (GCC) was associated with a tenfold increase in the odds of identifying patients likely to progress to definite ALS (OR 10 [1.39, 71.87], p = 0.02). DISCUSSION: Our results suggest that serum NfL is a robust complement to current ALS diagnostic criteria and shows potential to improve early identification and diagnostic certainty of patients likely to progress to definite ALS. Integrating serum NfL with GCC provided the strongest predictive model. These findings warrant larger multicenter, prospective studies to confirm results.