Objective:

Background:

The diagnostic value of CSF MOG-IgG testing remains uncertain, particularly when performed using commercially available fixed cell-based assays. We evaluated the diagnostic utility and cost of CSF MOG-IgG testing in patients with paired serum and CSF samples.

Design/Methods:

We performed a retrospective diagnostic accuracy study at a large academic center. Adult patients tested in serum and/or CSF from January 2024 to February 2026 were identified. Paired samples were serum and CSF obtained within 7 days. Serum testing used live CBA and CSF testing fixed CBA at external laboratories. Sensitivity, specificity, predictive values, and exact McNemar testing were calculated using serum as reference. Costs were estimated from vendor pricing.

Results:

Among 94 patients with paired testing, 17 (18.1%) were serum-positive. Of these, 14 were CSF-negative and 3 positive in both serum and CSF. No patient was CSF-positive while serum-negative. CSF sensitivity was 17.6% and specificity 100.0%. Mean estimated cost per CSF test was 632 USD, totaling 59,408 USD over 2 years.

Conclusions:

Commercially available fixed-CBA CSF MOG-IgG testing provided no incremental yield beyond serum testing in this cohort and incurred substantial cost. Unlike prior studies using live CBA, which showed higher sensitivity and detected CSF-restricted cases, our findings support limiting CSF testing to selected seronegative patients, ideally with live CBA.