Laboratory Test Guide

NMDA Receptor IgG Antibody with Reflex, Serum (Sendout)

General Information

Lab Name

NMDA Receptor IgG Antibody w/Reflex, Serum (Sendout)

Lab Code

RNMDAG

Epic Name

NMDA Receptor Ab, IgG W/Reflex, Serum (Sendout)

External Test Id

2004221

Description

Ordering Recommendation: Confirm diagnosis of anti-NMDAR encephalitis. May be used in monitoring treatment response in individuals who are antibody positive.

Test Algorithm: If the NMDA Antibody IgG is positive, then an NMDA Antibody IgG Titer is performed at additional charge.

Ordering Note: This test is for serum samples only. For NMDA-R Antibody testing on CSF, refer to NMDA Receptor IgG Antibody with Reflex, CSF (Sendout) [RCNMDA].

Synonyms

2004221, Anti NMDA, Anti-GluN1, Anti-NMDA, Anti-NR1, Glutamate Receptor Antibodies, Limbic Encephalitis, N-methyl-D-aspartate receptor, NMDA IgG, Paraneoplastic

Components

Code	Name
RNMDA	NMDA Receptor IgG Antibody w/Reflex, Serum (Sendout)
RNMDAR	NMDA Receptor IgG Antibody, Serum
UW424	Study: NMDA Receptor Abs, SRM

Interpretation

Method

Semi-Quantitative Cell-Based Indirect Fluorescent Antibody

Reference Range

See individual components

Ref. Range Notes

Reference Range:

< 1:10

Interpretive Data: NMDA receptor antibody is found in a subset of patients with autoimmune limbic encephalitis and may occur with or without associated tumor. Decreasing antibody levels may be associated with therapeutic response. In addition, positive results have been reported in patients with nonautoimmune phenotypes. A negative test result does not rule out a diagnosis of autoimmune limbic encephalitis. Results should be interpreted in correlation with the patients clinical history and other laboratory findings. Serum testing should be paired with CSF testing for improved diagnostic sensitivity.

This indirect fluorescent antibody assay utilizes full-length GluN1 transfected cell lines for the detection and semiquantification of NMDA receptor IgG antibody.

Guidelines

Autoimmune Encephalitis Testing Recommendations

Ordering & Collection

Specimen Type

Blood

Collection

6 mL blood in RED TOP tube or GOLD SST

Handling Instructions

Outside Laboratories: Centrifuge sample and transfer serum to a separate vial within 2 hours of collection. Refrigerate serum.

Stability: Refrigerated (preferred): 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles); Ambient: 48 hours.

Unacceptable Conditions: CSF or plasma. Contaminated, hemolyzed, or severely lipemic specimens.

Quantity

requested: 1 mL serum + 1 mL serum for UW424
minimum: 0.2 mL serum

Processing

Centrifuge sample and transfer 1 mL serum each into two separate plastic vials within 2 hours of collection. If sample volume is low, prioritize the sendout test (RNMDA).

UW424: Freeze serum at -20°C in Immunology rack.
RNMDA: Store serum in Sendouts Refrigerated ARUP rack.

Sendouts:

Order ARUP Test: 2004221
Interfaced: Yes [Interface: 602; Department: ARPR]