To establish the incidence of demyelination in patients who have received anti-tumor necrosis factor alpha (anti-TNFα) therapy, through analysis of adverse events reported in a prospective cohort of patients receiving biological therapies.
A cohort study was performed on prospectively acquired data via the British Society for Rheumatology Biologics Register in Rheumatoid Arthritis. All potential demyelinating events during follow-up were extracted and classified as definite, probable, or possible blinded to treatment data. The point of starting an anti-TNF therapy in individuals with no prior reported demyelination was the time of exposure. Crude rates of demyelination and standardized incident rates (SIRs) compared with the general UK population were calculated.
Thirty-five individuals with demyelinating events were identified from a total pool of 13,489. The median age at study entry was 44 years, and the median disease duration was 8 years; 71% were female. Events occurred a median of 3 (interquartile range 1-5) years from the start of the first anti-TNF therapy. Twenty-six events occurred in individuals still taking anti-TNFα therapy; of the other 9, 6 were within 90 days of drug withdrawal. The raw incidence of demyelination was 19.7/100,000 patient-years (95% CI 13.7-27.3). The SIR in the whole population was 1.38 (95% CI 0.96-1.92) and 0.83 (0.51-1.26) limited to definite/probable cases.
Demyelination following anti-TNF therapy is uncommon. Patients receiving anti-TNFα therapy show a marginally increased SIR; this is lost in sensitivity analyses. Patients concerned about anti-TNFα-associated demyelination can be relatively reassured by these data.