Method: We studied 83 patients with active RA treated with a TNF inhibitor (50 patients with IFX,and 33 with ADA), for a median of 4.3 (± 2.6) years. Clinical characteristics, serum trough drug levels and the presence of anti-drug Abs were evaluated. Clinical activity was measured by Disease Activity Score 28 (DAS28) and clinical response was evaluated by EULAR criteria. ACPA were measured by second generation ELISA, RF by nephelometry and the presence of anti-drug Abs by a bridging ELISA (1). Three time points (6 months, 1 year and 2-4 years) were chosen for the study. For the purpose of this study only patients with positive RF and/or ACPA were considered.
RF was positive in 79 (95.2%) patients and ACPA in 76 (91.6%) patients. Both drug group (IFX and ADA) were analyzed together because no differences were seen in the decrease of RF (p=0.108) and ACPA (p=0.888) levels between groups. At baseline, there was no association between clinical activity and ACPA and RF levels (Pearson correlation (PC)=0.21 and PC=0.25, respectively). At 6 months RF but not ACPA, showed a significant decrease (320.66±393.53 at baseline vs 181.26±239.60 at 6 months, p<0.001 in RF and 1537.82±1263.87 at baseline vs 1428.59±1278.33 at 6 months, p=0.239 in ACPA). At 1 year and 2-4 years, both RF and ACPA titers had a significant decrease (p<0.05).The relative change (%) was significantly higher for RF than for ACPA during all the study (p<0.0001). More patients became negative in RF than in ACPA levels along the study [7 out of 79 (8.8%) vs 5 out of 76 (6.5%) at 6 months (p=0.4), 19 out of 79 (24%) vs 4 out of 76 (5.2%) at 1 year (p=0.001), 21 out of 79 (26.5%) vs 4 out of 76 (5.2%) at 2-4 years (p=0.0001), respectively]. EULAR clinical response was not associated by the lost of positivity of RF and ACPA at any studied point (p>0.1). RF and ACPA levels were not affected by the development of anti-drug Abs (p=0.2 and p=0.62, respectively), concomitant MTX therapy (p=0.858 and p=0.588, respectively) and clinical EULAR response at 4 years (p=0.165 and p=0.537, respectively).
The anti-TNF therapy has an influence on RF and ACPA levels in RA patients in a long term treatment, being RF decrease more pronounced than the reduction of ACPA levels. The change in the RF and ACPA titers was not associated with a improvement in the clinical response.
(1) Pascual-Salcedo et al. Influence of immunogenicity on the efficacy of long-term treatment with infliximab in rheumatoid arthritis. Epub 22 March 2011
Disclosure: S. Baos, None; C. Plasencia, None; S. Ramiro, None; R. Moral, None; J. Díez, None; E. Martin-Mola, None; A. Balsa, None; D. Pascual-Salcedo, None.