relationship between trough levels of anti-infliximab and serum biomarkers in patients with rheumatoid arthritis

Rheumatoid arthritis is a chronic condition, characterized by the expression of antibody against self-antigens. inflammatory cell of synovial tissues secreted numerous cytokines, include tumor necrosis factor alpha. infliximab was designed to treat several autoimmune diseases. however, a considerable number of patients fail to respond appropriately. to investigate the relationship between trough infliximab serum levels and infliximab antibody with c-reactive protein (crp), rheumatoid factor (rf), and anticyclic citrullinated peptide (accp) status. this study examined 83 rheumatoid arthritis patients on infliximab for 6 months duration. sampling was collected in rheumatology unit at (baghdad teaching hospital) from september 2021 to april 2022. each patient had 3 ml of blood drawn. before the next dosage of medication. anti-infliximab antibody, trough infliximab, and accp levels were measured using elisa, while rf and crp status were determined using an agglutination test. ages of the patients ranged between 30-75 years old, (66 females and 17 males), and 44.6% of patients were smokers. in this study, 41 out of 83 patients were responder for infliximab therapy. the seropositivity of anti-drug antibodies was 50% in non-responder and 48.80% in responder patients. in contrast, the infliximab trough level classification as low and high in responder and non-responder patients was high in 56.1 %, and 40.5% of patients respectively. the difference between the two groups was statistically non-significant p=0.114. in addition, 74 patients tested positive for anti-cyclic citrullinated peptide. (89.2%), abnormal crp levels were found in 54 (65.1%) patients, and seropositivity of rheumatoid factor was found in 52 (62.7 %) of the patients. there was a negative relationship between smoking and responsiveness to infliximab. (r= -0.295 p 0.007) while there was a positive correlation between anti-infliximab antibodies with crp and rf (p=0.026). likewise, accp and serum trough infliximab levels were correlated significantly (p=0.014). antidrug antibody seropositivity correlates positively with crp and rf status and between accp and serum trough infliximab in ra patients while there is a negative correlation between smoking and early response to infliximab.