Phosphorylated Neurofilament Heavy Chain in Cerebrospinal Fluid and Serum as a Biomarker of Axonal Injury in Algerian Patients with Multiple Sclerosis

Objective: Axonal injury is a key determinant in irreversible disability in multiple sclerosis (MS). Reliable biomarkers of neuroaxonal damage are essential for improving diagnosis, monitoring disease progression, and evaluating treatment response. This study investigated the relationship between phosphorylated neurofilament heavy chain (pNF-H), clinical characteristics, and conventional cerebrospinal fluid (CSF) and serum biomarkers in Algerian patients with MS. Methods: A total of 102 participants were enrolled. Clinical, immunological, and biochemical parameters were assessed, including the Expanded Disability Status Scale (EDSS), oligoclonal bands (OCBs), IgG index, albumin quotient, and pNF-H concentrations in paired CSF and serum samples. Results: OCBs were detected in 85.5% of patients, and 65.21% exhibited intrathecal immunoglobulin synthesis, with a median IgG index of 0.87. Patients with progressive MS were significantly older and more disabled than those with relapsing–remitting MS (age: p = 0.01; EDSS: p = 0.0007). OCB-positive patients had significantly higher IgG index values (p = 0.0004), but OCB status was not associated with age, EDSS, or albumin quotient. EDSS correlated positively with age (p = 0.0007), albumin quotient (p = 0.01), and IgG index (p = 0.001). Both CSF and serum pNF-H levels were significantly elevated in MS patients compared with NSDs group (p < 0.001). Increased pNF-H concentrations were associated with progressive disease and greater disability (EDSS ≥ 5). Conclusions: Elevated pNF-H levels in CSF and serum are associated with disease severity and progressive MS, supporting their potential as complementary biomarkers of neuroaxonal damage and clinical disability in routine MS assessment.