Cartilage Oligomeric Matrix Protein Level in Rheumatic Diseases: Potential Use as a Marker for Measuring Articular Cartilage Damage and/or the Therapeutic Efficacy of Treatments

Cartilage oligomeric matrix protein (COMP) is a tissue-specific noncollagenous protein that was first detected in the serum and the synovial fluid of patients suffering from rheumatic disorders, such as rheumatoid arthritis, reactive arthritis, juvenile chronic arthritis, and osteoarthritis. In this review, the authors consider serum COMP levels in different diseases and discuss their study of patients with rheumatoid arthritis treated with anti-TNF-alpha, to evaluate whether COMP is able to predict a rapid and sustained clinical response to these drugs. They observe that patients with high COMP levels have a lower ACR 70 response independently of the state of systemic inflammation, and conclude that COMP seems to have a pathogenetic role that is independent of the mechanisms regulating inflammatory processes

Psoriatic arthritis: the role of self-reported non-adherence, non-trough drug levels, immunogenicity and conventional synthetic DMARD co-therapy in adalimumab and etanercept response

Objective The aim of this study was to assess the relationship between self-reported non-adherence, non-trough drug levels, immunogenicity and conventional synthetic DMARD (csDMARD) co-therapy in TNF inhibitor (TNF-i) drug response in PsA. Methods Serum samples and adherence questionnaires were collected at baseline, 3, 6 and 12 months for PsA patients prescribed TNF-i. Non-trough adalimumab (ADL) and etanercept (ETN) drug levels were measured at 3 and 6 months using commercially available ELISAs. Clinical response was assessed using PsA response criteria (PsARC) and change in 28-joint DAS (ΔDAS28) between baseline and 3, 6 and 12 months. Results In 244 PsA patients (52.5% ADL and 47.5% ETN), self-reported non-adherence was associated with PsARC non-response over 12 months using generalized estimating equation (GEE) modelling (P = 0.037). However, there was no significant difference between non-trough ADL or ETN drug levels based on self-reported non-adherence. Higher ETN levels at 3 months were associated with PsARC response at 3 (P = 0.015), 6 (P = 0.037) and 12 months (P = 0.015) and over 12 months using GEE modelling (P = 0.026). Increased ADL drug levels at 3 months were associated with greater ΔDAS28 at 3 months (P = 0.019). ADL anti-drug antibody-positive status was significantly associated with lower 3- and 6-month ADL levels (P < 0.001) and ΔDAS28 and PsARC response at 3, 6 and 12 months. Meanwhile, MTX co-therapy was associated with a reduction in immunogenicity at 3 and 6 months (P = 0.008 and P = 0.024). Conclusion Although both were associated with reduced response, the objectively measured non-trough drug levels showed more significant associations with drug response than self-reported non-adherence measures