When should MOG-Ab be tested in patients with suspected autoimmune encephalitis with seizures and normal MRI?

In someone with suspected autoimmune encephalitis with seizures and a normal MRI (presuming done with gadolinium and the optic nerves are well visualized), I would not obtain MOG. MOG testing would have a very low pretest probability (so low that a positive test might well be a false positive). If one suspects NMDA encephalitis or one of the other similar autoimmune encephalitides, I would obtain routine blood work, an LP with routine CSF studies, plus a PCR-based encephalitis panel, along with ...

In my opinion, it should be tested. MOGAD phenotype is expanding. I have recently seen a MOG Ab+ case presenting with encephalitis, seizure, and a normal MRI, abnormal PET brain.