Abstract: Background – There is no antemortem diagnostic test for canine degenerative myelopathy (DM). Hypothesis/Objectives – Determine the diagnostic accuracy of neurofilament light (NfL) concentration in serum and cerebrospinal fluid (CSF) for DM. Animals – Fourteen DM-affected (Stage 1, 2), 6 DM-mimic, and 17 neurologically normal dogs. Methods – Archived and prospectively collected serum and CSF NfL concentrations were measured using single-molecule array. Median concentrations were compared across groups via Kruskal-Wallis test with post-hoc Dunn’s method. Receiver operator characteristics (ROC) curves were generated. Results – Median serum NfL concentration was increased in DM dogs (104.4 pg/mL, IQR 80.24-119.2) compared to DM-mimics (27.03 pg/mL, IQR 6.424-42.46) (p = 0.0414) and neurologically normal dogs (7.412 pg/mL, IQR 1.421-27.57) (p = 0.0037). Median CSF NfL concentration was increased in DM dogs (8,241 pg/mL, IQR 5,737-28,710) compared to DM-mimics (1,458 pg/mL, IQR 785.4-1,669) (p = 0.0446) and neurologically normal dogs (1,485 pg/mL, IQR 271.5-2,370) (p = 0.0010). Serum NfL concentration greater than 53.4 pg/mL was 100% sensitive (Confidence Interval (CI) 64.57%-100%) and 91.67% specific (CI 64.61%-99.57%) for DM. The area under the ROC curve was 0.9762 (CI 0.9171-1.0). CSF NfL concentration greater than 3,731 pg/mL was 100% sensitive (CI 70.09%-100.0%) and 93.75% specific (CI 71.67%-99.68%) for DM. Area under the ROC curve was 0.9722 (CI 0.9124-1.0). Conclusions and Clinical Importance – Serum NFL concentration is a promising non-invasive diagnostic biomarker of DM that will aid clinical management of affected dogs.
