Cell-based assays for MOG-IgG detection have been found to have high but imperfect clinical specificity, leading to the potential for false positive results ( 11, 12).
Currently, MOG-AD is diagnosed when a patient presents with an accepted clinical demyelinating syndrome, has positive detection of MOG-IgG in serum by a validated assay, and does not fulfill criteria for another CNS demyelinating disease ( 6). Its course may be monophasic or relapsing-remitting, and in most cases, the disease is steroid-responsive but may relapse shortly after discontinuing such treatement ( 3). For example, when optic neuritis occurs in the setting of MOG-AD, it is typical to find extensive optic nerve T2 hyperintensity that is chiasm-sparing and with predominant anterior segment involvement on imaging ( 10). Distinct radiographic features of MOG-AD, differing from typical findings in MS, have been described in several studies ( 7– 10). Clinical manifestations include acute disseminated encephalomyelitis (ADEM), optic neuritis that is often bilateral and/or severe, transverse myelitis that may be short segment or longitudinally extensive, unilateral cortical FLAIR-hyperintense lesions in anti-MOG-associated encephalitis with seizures (FLAMES) ( 4)/unilateral cerebral cortical encephalitis (UCCE) ( 5), and brainstem encephalitis ( 3, 6). MOG-AD is a CNS demyelinating disorder that affects both pediatric and adult patients with a median age of onset in the fourth or fifth decade of life ( 3). The advent and further optimization of a live cell-based serum assay for detection of its diagnostic biomarker, MOG-IgG ( 1, 2), has permitted characterization of the clinical and radiographic spectrum of MOG-AD. Our understanding of the clinical spectrum of myelin oligodendrocyte glycoprotein antibody-associated disease (MOG-AD) is in its infancy when compared to better studied central nervous system demyelinating diseases, such as multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). The presence of positive cases with and without demyelinating features, emphasizes a need for testing in the appropriate clinical context, analysis of titer value and clinical interpretation. In our cohort, the PPV for MOG-IgG improved utilizing a titer cut-off of ≥1:40. Validated diagnoses of the remaining positive patients without MOG-AD included: migraine ( n = 2, titers 1:20, 1:100), inclusion body myositis ( n = 1, titer 1:100), autoimmune encephalitis ( n = 2, titers 1:20, 1:20), hypoxic ischemic brain injury ( n = 1, titer 1:20), IgG4-related disease ( n = 1, titer 1:20), and idiopathic hypertrophic pachymeningitis ( n = 1, titer 1:20). The treating diagnosis for one RRMS patient with a 1:40 titer was subsequently modified to MOG-AD by treating neurologists. Three MOG positive cases had a prototypical multiple sclerosis diagnosis (RRMS n = 2, titers 1:20 and 1:40 PPMS n = 1 1:100). Using a ≥1:40 titer cutoff, 65 (3.5%) tested positive and PPV was 93.8%. Of 1,877 patients tested, 78 (4.2%) patients tested positive for MOG-IgG with titer ≥1:20, and of these, 67 had validated MOG-AD yielding a PPV of 85.9%. MOG-IgG positive cases were reviewed for fulfillment of typical MOG-AD clinical features, determined by treating neurologists and study authors.
All were tested via the MOG-IgG1 fluorescence-activated cell sorting assay (Mayo Laboratories, Rochester, MN). The Massachusetts General Brigham Research Patient Data Registry database was queried for patients with positive serum MOG-IgG detection, at least once, between Januand March 25, 2021. In this real-world institutional cohort study, we determined the PPV of serum MOG-IgG for clinically defined MOG-AD in our patient population. PPV may vary depending upon the tested population, thus supporting further investigation of MOG-IgG testing at other centers. The positive predictive value (PPV) of MOG-IgG testing by live cell-based assay was reported to be 72% in a study performed at the Mayo Clinic using a cut-off of 1:20. Myelin oligodendrocyte glycoprotein antibody associated disease (MOG-AD) is a CNS demyelinating disease, typically presenting with optic neuritis, transverse myelitis, and/or ADEM-like syndromes. 2Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States.1Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States.Klawiter 1 Tanuja Chitnis 2 Michael Levy 1 Marcelo Matiello 1
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