CTHRC1 as a New Biomarker in Diagnosis of Rheumatoid Arthritis and Its Role in Seronegative Patients.

Rheumatoid arthritis (RA) is a chronic, progressive, autoimmune disease of synovial joints. Disease progression is characterized by periods of high disease activity involving both, a systemic immune response and tissue-specific inflammatory events that may lead to joint and bone destruction and subsequent disability.

Rheumatoid arthritis is a multifactorial disease with significant contribution from genetic and non-genetic factors that together account for complex disease pathology.

Diagnosis of RA is based mainly on detection of high titers of rheumatoid factor (RF) and of antibodies against cyclic citrullinated peptide (anti-CCP) or against citrullinated protein (ACPA).

The major RF species could be detected only in 60-70% of RA patients; patients with high levels of RF have higher disease activity with greater disabilities.

The problem is that RF is not a specific marker for RA and is often absent in early stages of the disease, on the other hand ACPA and CCP auto antibodies provide high specificity but moderate sensitivity, adding to that CRP and ESR are general indicators of inflammation and are not specific for RA.