THURSDAY, March 12 (HealthDay News) -- Biomarkers that can be detected before women develop rheumatoid arthritis (RA) have been identified by U.S. researchers.

Elizabeth Karlson, of Brigham and Women's Hospital and Harvard Medical School, and her colleagues examined blood samples taken from 170 participants in the Women's Health Study and the Nurses' Health Study. The women had no symptoms of RA when the blood samples were taken but later developed the disease.

The researchers found that levels of two cytokines (proteins released by the immune system) called tumor necrosis factor (TNF) and interleukin-6 (IL-6) were elevated before the women developed RA symptoms. Levels of both cytokines are elevated in people with active RA.

Because TNF degrades rapidly in stored blood samples, the researchers used soluble tumor necrosis factor receptor II (sTNFRII) as a surrogate. Levels of sTNFRII were elevated up to 12 years before development of RA symptoms and were associated with a twofold increased risk of RA. Levels of IL-6 were elevated about four years before the onset of RA symptoms.

"Our findings suggest that during the preclinical phase of autoantibody production, there is immune reactivity, with production of proinflammatory cytokines that are typically seen in symptomatic RA, namely IL-6 and TNF," the researchers wrote.

Screening for biomarkers could be used for RA risk counseling and for targeted therapies to prevent the disease, they suggested.

The study was published in the March issue of Arthritis & Rheumatism.

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