Serum neurofilament light chain as a prognostic biomarker of glial fibrillary acidic protein autoimmunity

This study investigated whether serum neurofilament light chain (NFL) levels could predict the prognosis of patients with Glial Fibrillary Acidic Protein Autoimmunity (GFAP-A). The study included 54 patients diagnosed with GFAP-A at Gifu University Graduate School of Medicine between June 2019 and October 2023. Patients with other neurological diseases or antineuronal antibodies were excluded. NFL levels in serum and cerebrospinal fluid (CSF) samples at admission were measured, and their association with patient prognosis was analyzed. Patients with an unfavorable outcome were defined as those with a modified Rankin Scale (mRS) score of 3 or higher at 6 months after admission. Results showed that 13 patients (24 %) had an unfavorable outcome. Serum NFL levels at admission were higher in patients with an unfavorable outcome [median (range): 191 (39–409) pg/mL] compared to those with a favorable outcome (mRS score ≤ 2) [64 (14–341) pg/mL] (P < 0.001). Similarly, CSF NFL levels were higher in patients with a poor prognosis [21,932 (9673–34,324) pg/mL] compared to those with a favorable outcome [8014 (986–55,130) pg/mL] (P < 0.001). Binary logistic regression analysis, adjusted for age, duration from onset to admission, and mRS score at admission, identified serum NFL level as an independent predictor of unfavorable outcome at the 6-month time point (OR, 1.0114; 95 % CI [1.0014–1.0214]; P = 0.0250). ROC analysis indicated that serum NFL level at admission is a sensitive predictor of unfavorable outcome for GFAP-A (AUC, 0.853; sensitivity, 92.3 %; specificity, 73.2 %). In conclusion, serum NFL levels at diagnosis may serve as an important prognostic biomarker for GFAP-A.