High albumin level is a predictor of favorable response to immunotherapy in autoimmune encephalitis.

There is no known biomarker that predicts the response to immune therapy in autoimmune synaptic encephalitis. Thus, we investigated serum albumin as a prognostic biomarker of early immune therapies in patients with autoimmune encephalitis. We enrolled patients who were diagnosed with definite autoimmune encephalitis and underwent IVIg treatment at Seoul National University Hospital from 2012 to 2017. Patients were dichotomized according to serum albumin prior to IVIg administration with a cut-off level of 4.0 g/dL, which was the median value of 50% of patients. Seventeen (53.1%) of the 32 patients with definite autoimmune encephalitis who received IVIg treatment in our hospital had low serum albumin (<4.0 g/dL). The initial disease severity (mRS ≥ 4) was the sole factor that predicted low albumin in autoimmune encephalitis patients using multivariate analysis (P = 0.013). The low albumin group exhibited a worse response to immune therapy at the third and fourth weeks from IVIg administration (P < 0.01 and P = 0.012, respectively), and recovery to activities of daily life without assistance was faster in the high albumin group (log-rank test for trend, P < 0.01). Our study found that pretreatment low serum albumin was a significant indicator of autoimmune encephalitis prognosis in the short-term and long-term.