Urinary neopterin: A novel biomarker of disease progression in amyotrophic lateral sclerosis

Background and purpose The aim was to evaluate urinary neopterin, a marker of pro‐inflammatory state, as a potential biomarker of disease prognosis and progression in amyotrophic lateral sclerosis (ALS); and to compare its utility to urinary neurotrophin receptor p75 extracellular domain (p75ECD). Methods This was an observational study including 21 healthy controls and 46 people with ALS, 29 of whom were sampled longitudinally. Neopterin and p75ECD were measured using enzyme‐linked immunoassays. Baseline and longitudinal changes in clinical measures, neopterin and urinary p75ECD were examined, and prognostic utility was explored by survival analysis. Results At baseline, urinary neopterin was higher in ALS compared to controls (181.7 ± 78.9 μmol/mol creatinine vs. 120.4 ± 60.8 μmol/mol creatinine, p = 0.002, Welch's t test) and correlated with the Revised ALS Functional Rating Scale (r = −0.36, p = 0.01). Combining previously published urinary p75ECD results from 22 ALS patients with a further 24 ALS patients, baseline urinary p75ECD was also higher compared to healthy controls (6.0 ± 2.7 vs. 3.2 ± 1.0 ng/mg creatinine, p