A Comparative Study of 141 Glial Fibrillary Acidic Protein Immunoglobulin G Positive Cases.

Background: Glial fibrillary acidic protein-immunoglobulin G (GFAP-IgG) positivity is associated with autoimmune GFAP astrocytopathy (GFAP-A), but also with other autoimmune encephalitides and viral infections. We attempted to elucidate the characteristics of GFAP-A in relation to other GFAP-IgG-positive encephalitides and constructed a differential diagnosis model.

Methods: 141 GFAP-IgG-positive cases were identified, including 52 astrocytopathy (GFAP-A group), 48 autoimmune encephalitis (AE-G), and 41 viral encephalitis (VE-G). Multivariate logistic regression was employed to create a diagnostic model, with validation using an external cohort.

Result: Compared to the AE-G group, the GFAP-A patients showed more onset age ≥ 50 years, headache, fever, consciousness disturbance, MRI radial vascular enhancement, cerebrospinal fluid (CSF) antibody titer grade ≥ 4, and CSF proteins ≥ 700 mg/L, but less female sex, limb numbness, visual disturbances, and CSF chloride ≤ 120 mmol/L. Among these, CSF antibody titer grade ≥ 4, CSF protein ≥ 700 mg/L, and absence of visual disturbances were independent risk factors for GFAP-A diagnosis. Compared to the VE-G group, the GFAP-A patients showed more course ≥ 14 days, onset age ≥ 50 years, limb weakness, serum potassium ≤ 3.9 mmol/L, CSF antibody titer grade ≥ 4, CSF leukocytes ≤ 46*10, MRI radial vascular enhancement, MRI involvement of brainstem, and MRI involvement of spinal cord, but less headache, fever, nausea, and vomiting. Among these, serum potassium ≤ 3.9 mmol/L, MRI spinal cord involvement, and absence of nausea and vomiting were independent risk factors for GFAP-A diagnosis.

Conclusions: Based on critical clinical indicators identified, we constructed a differential diagnosis model for GFAP-A.