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Updated: May 13, 2026

A Simple Cell-based Immunofluorescence Assay to Detect Autoantibody Against the N-Methyl-D-Aspartate (NMDA) Receptor in Blood
Published on: January 9, 2018
Anti-NMDA-receptor antibody encephalitis: performance evaluation and laboratory experience with the
Brenda B Suh-Lailam1, Thomas R Haven, Susan S Copple
1ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, United States.
Background:
Antibodies targeting the NR1 subunit of the N-methyl-d-aspartate-receptor (NMDAR) are considered diagnostic for a novel form of autoimmune encephalitis. We report the validation of a qualitative indirect immunofluorescence antibody (IFA) test for the detection of anti-NMDAR IgG and describe the attributes of antibody-positive patients.
Methods:
The anti-NMDAR IgG assay (Euroimmun Diagnosika, Lübeck, Germany) was validated with serum and cerebrospinal fluid (CSF) specimens from 30 healthy and 50 disease controls as well as 5 anti-NMDAR IgG-positive individuals. Consecutive specimens (n=1671) for anti-NMDAR IgG antibodies were evaluated and positive specimens titrated to end-point [starting dilutions: CSF; 1:1 and serum; 1:10]. In a subset of antibody-positive patients, we sought clinical information for correlation with diagnostic and treatment outcomes.
Results:
The assay demonstrated excellent performance characteristics in all groups evaluated. Of the 1671 specimens tested, 1389 were unique cases with a positivity rate of 9.0% (n=123). For the antibody-positive samples, the female to male ratio was 2:1 with a prevalence of 46% in the pediatric population (≤17 years). Antibody titers were titrated to end-point for 106/123 specimens [45 CSF, 41 sera, and 20 CSF and serum pairs] with more than 75% having titers greater than 1:10 (CSF) and 1:20 (serum). Overall, high levels of these antibodies showed correlation to disease severity with variable response to treatment in the subset of patients evaluated.
Conclusion:
Our data suggests a high prevalence for anti-NMDAR antibody encephalitis irrespective of age and gender in our unselected disease cohort with support for measuring antibody titers in the evaluation of these patients.
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