MOG and myeloid sarcoma: In addition to variable sensitivity across in-house live CBAs, there may also be variable specificity; this is reflected by MOG-IgG positivity rates by live CBA in MS that range from 0.3% to as high as 9.9% exceptionally in one study, acknowledging that these differences may relate in part to how patients with MS are selected across studies and not solely assay performance.14,15 Taken together, these findings highlight the value of MOG-IgG live CBA performed at specialized centers that have expertise in this methodology and published assay performance data confirming high diagnostic accuracy.