Journal
RHEUMATOLOGY
Volume 55, Issue 11, Pages 2050-2055Publisher
OXFORD UNIV PRESS
DOI: 10.1093/rheumatology/kew299
Keywords
immunogenicity; anti-drug antibodies; adalimumab; anti-TNF; TNF-inhibitors; ELISA; RIA; drug levels; therapeutic drug monitoring; human anti-human antibodies
Categories
Funding
- North West England Medical Research Council
- Medical Research Council [G1000417/94909, G1000417/ 94909]
- ICON
- GlaxoSmithKline
- AstraZeneca
- Medical Evaluation Unit
- Arthritis Research UK [20385, 20830]
- NIHR Manchester Musculoskeletal Biomedical Research Unit
- National Institute for Health Research Biomedical Research Unit
- MRC [G1000417, G1001518] Funding Source: UKRI
- Medical Research Council [G1000417, G1001518] Funding Source: researchfish
- National Institute for Health Research [CL-2006-06-010, CL-2015-06-005] Funding Source: researchfish
- Versus Arthritis [20747] Funding Source: researchfish
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Objective. To determine the concordance between RIA and bridging ELISA at detecting anti-drug antibodies (ADAbs) in the context of random adalimumab levels and investigate the additional clinical utility of detecting ADAbs in RA patients who test ADAb positive by RIA and negative by ELISA. Methods. ADAb levels were determined using RIA and bridging ELISA in 63 adalimumab-treated RA patients (159 samples). Immunogenicity concordance was determined using receiver operating characteristic curves. To determine the additional clinical value provided by a positive RIA in the presence of negative ELISA, association between treatment response (Delta DAS28), adalimumab drug levels and ADAbs was evaluated longitudinally using generalized estimating equation. Results. Of the 60 RIA(+) samples (n = 31 patients), 19 (n = 10 patients) were also ELISA(+), corresponding to 31.7% of samples. Area under the curve for detecting ADAbs using ELISA (compared with RIA) using receiver operating characteristic curves was 0.65 (95% CI: 0.59, 0.71); this increased to 0.91 (95% CI: 0.81, 0.99) if ADAbs were a (c) 3/4100 AU/ml using RIA. In RIA(+)/ELISA(-) patients, adalimumab levels were associated with Delta DAS28 over 12 months [regression coefficient: 0.098 (95% CI: 0.043, 0.15), P < 0.0001] and while ADAbs were significantly associated with drug level, they were not directly associated with Delta DAS28 over 12 months [beta coefficient: 0.00083 (95% CI: -0.0038 to 0.0054), P = 0.72]. Conclusion. ADAbs were detected using ELISA more frequently when present in high titres as measured by RIA. In RIA(+)/ELISA(-) patients, only drug levels were significantly associated with treatment response. Although ADAbs were not independently associated with treatment response, they may be helpful in determining the aetiology of low drug levels.
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