Swedish researchers say a blood test could predict rheumatoid arthritis (RA) long before the person notices any symptoms of the condition. The scientists say the blood test can detect levels of substances in the blood known as cytokines, chemokines, as well as other biochemical factors that increase years before the onset of RA. Research suggests that the early detection of the disease makes RA patients less likely to suffer joint damage and more likely to be able to lead an active life.