Immunoglobulin gamma autoantibodies directed against myelin oligodendrocyte glycoprotein (MOG-IgG) are associated with specific neurological syndromes, most frequently acute disseminated encephalomyelitis, optic neuritis and longitudinally extensive transverse myelitis.1 For all neurological surface-directed autoantibodies, including MOG-IgG, serum concentrations are higher than cerebrospinal fluid (CSF), consistent with their peripheral generation. Hence, in the UK, CSF testing is not routine in clinical practice. However, recent studies have reported patients with CSF MOG-IgG but without detectable serum MOG-IgG.2 3 The prevalence and clinical relevance of this finding is unclear. We aimed to address this by analysing MOG-IgG results in all paired serum and CSF samples from our national testing database.
We audited the database of MOG-IgG cell-based assay (CBA) requests from the Oxford Autoimmune Neurology Diagnostic Laboratory between 2011 and 2019. These data encompassed all samples referred to the centre for MOG-IgG testing by physicians over this time…