High IgA rheumatoid factor levels are associated with poor clinical response to tumour necrosis factor α inhibitors in rheumatoid arthritis

Adalimumab; Adult; Aged; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antirheumatic Agents; Arthritis, Rheumatoid; Autoantibodies; Biomarkers; Etanercept; Female; Humans; Immunoglobulin A; Immunoglobulin G; Infliximab; Male; Middle Aged; Peptides, Cyclic; Prospective Studies; Receptors, Tumor Necrosis Factor; Rheumatoid Factor; Severity of Illness Index; Treatment Outcome; Tumor Necrosis Factor-alpha; Rheumatology; Immunology