(P-TA-8) Plasmapheresis reduces titre of antibodies (anti-MOG and anti-AQP4) in optic neuritis, but clinical impact is unclear

Optic neuritis is an autoimmune disease characterized by ocular pain and vision loss.  Autoimmune laboratory evaluation includes anti-AQP4(anti-NMO) and anti-MOG antibodies in addition to clinical criteria for diagnosis.  Multimodal approaches to therapy include therapeutic plasma exchange (TPE) for rapid antibody reduction, as an adjunct to medical therapies.  Although theoretically expected, the quantitative effect of TPE on circulating antibody titres has not been demonstrated.  

Study

Design/Methods:

We reviewed anti-NMO, -MOG (Abs) serum results from 1/1/2017-5/1/2024 in 3493 patients who presented with visual loss.  TPE was performed after TM service consultation, prompted by a request from the primary neurology service, and at the discretion of the TM consultants.  Additional medications were continued per clinical orders. The patients in this case series were identified retrospectively via an EPIC query. The study population incudes patients receiving care at our healthcare system, including two academic medical centers, between 2017 and 2024 who had NMO or MOG antibody tests performed.  Titre "levels" were defined as the steps reported by the performing laboratory (see Table).  A comparison group consisting of patients with two antibody results within 30 days who did NOT undergo TPE was generated, to match the TPE patients (who had paired samples within that timeframe).  An ANOVA was performed to compare the mean titre differences between the TPE and no TPE groups.

Results/Findings:

14 patients had pre- and post-TPE titres for anti-NMO or anti-MOG.  Only 6 of these patients had antibodies drawn within a 30-day interval during TPE treatments.  37 patients had two antibody levels within 30 days and did NOT have TPE.  The difference between the later titre and the prior titre was defined as the "titre delta.  Negative numbers represent a decrease in the titre step.  Patients who had TPE had a significantly greater decrease in titre step compared to patients who did not undergo TPE:  (Means of -1 vs. -0.15, ANOVA p-value=0.047).  The median titre step decrease was -1 for patients undergoing TPE but was unchanged for patients who did not undergo TPE.

Conclusions:

As hypothesized, TPE did decrease the 30-day titre step for patients with optic neuritis.  However, indications for TPE typically hinge on patient symptoms, and even seronegative optic neuritis patients may show a response to TPE.  Our preliminary data demonstrate that the antibody reduction in patients who undergo a TPE series is one titre step.  Current and future work correlating clinical variable such as visual acuity are ongoing to determine if that one titre step decrease has clinical importance.