Background The identification of biomarkers able to improve the differential diagnosis between multiple sclerosis (MS) and neuromyelitis optica (NMO) is challenging because of a different prognosis and response to treatment. Growing evidence indicates that brain and CSF N-acetyl aspartate (NAA) concentration is a useful marker for characterising different phases of axonal pathology in demyelinating diseases, and preliminary studies suggest that increased serum NAA levels may be a telltale sign of acute neuronal damage or defective NAA metabolism in oligodendrocytes.
Objective To evaluate whether serum and CSF NAA concentration differs in patients with MS and NMO.
Design Observational, multicentre, prospective, cross sectional study.
Methods Serum samples were collected from 48 relapsing–remitting MS, 32 NMO and 76 age matched healthy controls. Coeval CSF samples were available for all MS and for 8/32 NMO patients. NAA was measured in serum and CSF by liquid chromatography–mass spectrometry.
Results MS patients showed higher serum and CSF NAA levels than NMO patients, and higher serum NAA levels than healthy controls (p<0.001). High serum NAA values, exceeding the 95th percentile of serum NAA values in healthy controls, were found in 100% of patients with MS and in no patient with NMO. No differences in serum NAA levels were found between NMO and healthy controls. In MS, serum and CSF NAA levels correlated with disability score.
Conclusions Determination of serum and CSF NAA levels may represent a suitable tool in the diagnostic laboratory workup to differentiate MS and NMO.
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Funding This work was supported by annual research grants from the Italian University and Apulia Region grant Progetto Strategico APQ Ricerca PS124 (Neurobiotech).
Competing interests CT received honoraria for consultancy or speaking from Sanofi-Aventis and Biogen. MPA received honoraria for speaking from Merck Serono and Biogen, and research grants from Sanofi-Aventis, Merck Serono, Biogen and Bayer Schering. AG received honoraria for speaking from Bayer Schering and Merck Serono, and research grants from Sanofi-Aventis. AL received honoraria for speaking from Biogen and research grants from Sanofi-Aventis, Merck Serono, Biogen and Bayer Schering. FP received honoraria for speaking from Sanofi-Aventis and Merck Serono. PL received research grants from Sanofi-Aventis, Merck Serono and Biogen. MT received honoraria for consultancy or speaking from Sanofi-Aventis, Biogen and Bayer Schering, and research grants from Merck Serono.
Ethics approval Ethics committee approval was obtained from each centre included in the study.
Provenance and peer review Not commissioned; externally peer reviewed.