Preliminary findings of a ‘test bundle’ to accelerate the diagnosis of MS and NMOSD following optic neuritis

•Minimizing the time between optic neuritis (ON) and downstream diagnoses (MS/NMOSD) needs urgency since early diagnosis equals early treatment.•Approximately 20 % - 23 % of MS diagnoses occurred > 6 months (delayed) after a diagnosis of ON.•Routine serum testing for NMOSD risks false-positive/negative results and hence, an accurate diagnosis of ON is sine qua non prior to performing further testing for associated diseases.•Prospective studies to confirm or refute our findings are needed to advance the concept of a rapid diagnosis of MS/NMOSD following ON. No study has investigated the length of time it takes to diagnose multiple sclerosis (MS) or neuromyelitis optic spectrum disorder (NMOSD, aquaporin 4 antibody disease or myelin oligodendrocyte glycoprotein antibody disease, MOGAD) following the onset of de novo optic neuritis (ON). Minimizing the time between ON and downstream diagnoses needs urgency since early diagnosis equals early treatment. The time elapsed from ON to a subsequent diagnosis of MS/NMOSD was estimated through analysis of retrospective data collected from the Axon Registry (AR) of the American Academy of Neurology (AAN) and from the University of Kentucky (UK), Lexington. The time to diagnose MS/NMOSD was arbitrarily set as occurring < 6 months (early) or > 6 months (delayed) following ON. Data was collected between 2007 and 2021 (AR) and 2012 to 2022, for UK, respectively. Of the 4015 ON patients from the AR dataset, 1069 (26.6 %) were diagnosed with MS, with 857 (80.2 %) diagnosed < 6 months (early) and 212 (19.8 %) diagnosed after > 6 months (delayed). Secondly, 420/4015 (10.4 %) were diagnosed with NMOSD (either MOGAD or AQP4 antibody disease), of which 340/420 (80.9 %) were diagnosed < 6 months (early) and 80/420 (19 %) diagnosed > 6 months (delayed). In the UK dataset, a total of 90/1464 individuals (6.14 %) were diagnosed with MS; of these, 69 patients (76.7 %) were diagnosed at < 6 months (early) and included a sub-group of 25 (27.8 %) diagnosed < 4 weeks; 21 (23.3 %) were diagnosed > 6 months (delayed) following ON. In either dataset (AR or UK, between 20 % - 23 % of MS diagnoses occurred > 6 months (delayed) after a diagnosis of ON. An accelerated diagnosis (4 weeks or less) of MS/NMOSD following ON in the UK data suggests that it is possible to minimize the time to a downstream diagnosis if a ‘test bundle’ of MRI of orbits, brain, C-spine, cerebrospinal fluid (CSF) analysis, and serum testing for NMOSD is used. Additional s