Neurofilament light chain in serum for the diagnosis of amyotrophic lateral sclerosis

<p><strong>Objective </strong>To determine the diagnostic and prognostic performance of serum neurofilament light chain (NFL) in amyotrophic lateral sclerosis (ALS).</p> <p><strong>Methods </strong>This single-centre, prospective, longitudinal study included the following patients: 124 patients with ALS; 50 patients without neurodegenerative diseases; 44 patients with conditions included in the differential diagnosis of ALS (disease controls); 65 patients with other neurodegenerative diseases (20 with frontotemporal dementia, 20 with Alzheimer&rsquo;s disease, 19 with Parkinson&rsquo;s disease, 6 with CreutzfeldtJakob disease (CJD)). Serum NFL levels were measured using the ultrasensitive single molecule array (Simoa) technology.</p> <p><strong>Results</strong>&ensp;Serum NFL levels were higher in ALS in comparison to all other categories except for CJD. A cut-off level of 62 pg/mL discriminated between ALS and all other conditions with 85.5% sensitivity (95%&thinsp;CI 78% to 91.2%) and 81.8% specificity (95%&thinsp;CI 74.9% to 87.4%). Among patients with ALS, serum NFL correlated positively with disease progression rate (rs =0.336, 95%&thinsp;CI 0.14 to 0.506, p=0.0008), and higher levels were associated with shorter survival (p=0.0054). Serum NFL did not differ among patients in different ALS pathological stages as evaluated by diffusion-tensor imaging, and in single patients NFL levels were stable over time.</p> <p><strong>Conclusions&ensp;</strong>Serum NFL is increased in ALS in comparison to other conditions and can serve as diagnostic and prognostic biomarker. We established a cut-off level for the diagnosis of ALS.</p>