Serum Glutamate as a Biomarker in NMO and MS

Neuromyelitis Optica (NMO) is an autoimmune disease that predominantly affects the optic nerves and the spinal cord. It was previously regarded as a variant of multiple sclerosis (MS) and still the distinction between both can sometimes be challenging. Our objective was to evaluate the potential usefulness of serum glutamate as a biomarker in distinguishing NMO from MS patients. This cross-sectional study included 20 NMO patients, 30 MS patients and 20 matched healthy controls. • Group 1: Twenty NMO patients who were diagnosed according to the revised diagnostic criteria of the International Panel for NMO Diagnosis (IPND), the twenty NMO patients were further subdivided to: Group 1a: twelve patients without recent relapses in the last 3 months Group 1b: eight patients with recent relapses in the last 3 months • Group 2: Thirty clinically definite MS (CDMS) patients diagnosed according to revised McDonald criteria 2017 all of them were relapsing remitting MS (RRMS), they were further subdivided into: Group 2a: Fifteen patients without recent relapses in the last 3 months Group 2b: Fifteen patients with recent relapses in the last 3 months • Group 3 Twenty healthy control Serum glutamate was significantly higher in NMO patients without relapse (16.78 ± 7.38 μg/mL) and NMO patients with relapse (18.40 ± 11.17 μg/ml) compared to controls (3.37 ± 1.28 μg/ml, P < 0.01 for both). The serum glutamate was also significantly higher in NMO patients without relapses (16.78 ± 7.38 μg/mL), as compared to MS patients without relapses (10.84 ± 3.26 μg/ml, P=0.005).Cutoff value of > 10.3 μg/mlwas found to predict diagnosis of NMO rather than MS in patients without relapses (sensitivity 83.33 % and specificity 60 %, p = 0.008). The level of glutamate was significantly higher in NMO patients and MS patients compared to healthy controls. Moreover, there was a significant higher level of serum glutamate in NMO patients without relapses when compared with MS patients without relapses, however no such significant difference was found between NMO patients in relapses and MS patients in relapses. Glutamate serum was significantly higher during relapse in MS patients when compared with MS patients without recent relapses.