Last updated: October 8, 2014
CPT Codes: 86431, 86200, 83520
Description: 14-3-3η (eta) is a new test that may be useful in diagnosing patients with early undifferentiated polyarthritis or may be a marker for those who have a greater risk of developing rheumatoid arthritis (RA) or erosive arthritis. 14-3-3η is one isoform from a family of chaperone proteins involved in intracelluar and extracelluar signaling. 14-3-3η is not known to have a pathogenic role in RA but has been shown to induce numerous proinflammatory mediators.
Method: Enzyme Linked Immunosorbent Immunoassay (ELISA) to detect the presence of the human protein, which is is 246 amino acids in length and has a molecular weight of 28.2 kDa. Serum assays for 14-3-3η are commercially avaialable. Antibody assays to detect anti-14-3-3η antibodies are not commercially available but have been positive in
Normal Values: Normal values are <0.2 ng/mL done by ELISA. Values are not affected by age.
Increased in: Early or established rheumatoid arthritis or psoriatic arthritis patients with erosive disease. In one study nearly two-thirds of early RA patients were positive for 14-3-3η and showed an overall sensitivity 77% and specificity of 93%. Patients with elevated levels are more likely to have more severe disease with more radiographic damage or potential for radiographic progression. 14-3-3η levels do not correlate with acute phase reactant levels (ESR, CRP) or disease activity scores and weakly correlate with RF and CCP antibody levels.
Normal in: Negative/normal values would be expected in other rheumatic disorders like including psoriasis, osteoarthritis, gout, systemic lupus erythematosus, Sjögren’s syndrome, scleroderma, inflammatory bowel disease and fibromyalgia.
Indications: This assay may be useful (along with with rheumatoid factor (RF) and cyclic citrullinated peptide (CCP) antibody testing) in patients with early undifferentiated inflammatory arthralgias or arthritis. As 14-3-3η does not correlate with CRP or DAS-28 activty scores, it is unlikely to be useful as a serial biomarker in RA management.
Maksymowych WP, van der Heijde D, Allaart CF, Landewé R, Boire G, Tak PP, Gui Y, Ghahary A, Kilani R, Marotta A. 14-3-3η is a novel mediator associated with the pathogenesis of rheumatoid arthritis and joint damage. Arthritis Res Ther 2014;16:R99. PMID: 24751211