Background/Purpose:

Infliximab (IFX) is a chimeric monoclonal antibody against tumor necrosis factor alpha (TNF-a). It is known to be effective and often used in the treatment of juvenile idiopathic arthritis (JIA) and /or chronic iritis. It is known that children on IFX therapy may develop serum antibodies to IFX. The presence of serum IFX antibodies may potentially decrease effectiveness of IFX therapy and may be associated with severe systemic allergic reactions. The purpose of our study was to determine whether the regular monitoring of IFX serum and antibody levels may be a useful clinical tool in the management of JIA and iritis patients receiving IFX.

Methods:

The study was a single center retrospective chart review of 28 JIA and/or chronic iritis patients who received intravenous IFX from 3/15-5/17. Data was recorded prior to each infusion, which varied from one to a maximum of 17 infusions per patient, regarding diagnosis, age, IFX dose and frequency, IFX serum and antibody levels, methotrexate and/or leflunomide dose and route, active arthritis joint count, chronic iritis and/or worsening iritis, antinuclear antibody, rheumatoid factor, cyclic citrullinated peptide antibody, erythrocyte sedimentation rate, and c-reactive protein (CRP). A generalized linear mixed model for longitudinal binary data was used to predict the outcome variables.

Results:

A total of 19 female and 9 male patients were included in our sample, mean (SD) age was 15 (4.5). See Table I for characteristics of study patients. While patients with arthritis develop antibodies, it appears that the clinical effects of the antibodies are only seen in the iritis patients. Anti-IFX antibodies significantly predict active iritis (p=0.05) and worsening iritis (p=0.0079); with each one hundred unit increase in anti-infliximab antibodies, the odds of active iritis increase by 16% and the odds of worsening iritis increase by 29%. Increased CRP significantly predicted active iritis (p=0.03) and worsening iritis (p=0.014); with each increase in 0.5mg of CRP/L, the odds of active iritis and worsening iritis are increased by 36% and 48%, respectively. Advancing age significantly predicted decreased incidence of active iritis (p=0.0005) and worsening iritis (p=0.0028); with each one year increase in age, the odds of active iritis and worsening iritis are decreased by 15% and 19%, respectively.

Conclusion:

Monitoring anti-IFX antibodies during IFX therapy appears to be useful in the management of IFX therapy in pediatric patients with iritis. Our results indicate that younger age and rising CRP are associated with increased incidence of active iritis and may be a useful alert in managing patients with iritis. Future research with a larger sample and prospective design will be needed to confirm the relationships among the variables found herein.

Table I – Characteristics of Study Group – N = 28

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/measurement-of-serum-infliximab-and-antibody-levels-as-an-adjunct-to-clinical-decision-making-regarding-infliximab-therapy/