Blood test could soon predict rheumatoid arthritis risk

A marker that can indicate the likelihood of a person developing rheumatoid arthritis 16 years before the condition takes effect has been identified by a team from Oxford University. The finding means that a blood test that looks for antibodies that recognise a particular protein called tenascin-C could reliably show those who will develop the condition.
When inflammation occurs in the body, particular proteins are altered (which is called citrullination). These altered proteins can generate an immune response from the body, which can see it turning antibodies on itself, causing rheumatoid arthritis.

Tests that spot antibodies to citrullinated proteins are already used to diagnose the disease. Tests for individual proteins usually have a relatively low diagnostic sensitivity, but a more general test called CCP, that detects synthetic citrullinated peptides, identifies a lot more cases.

“We knew that tenascin-C is found at high levels in the joints of people with rheumatoid arthritis,” says Dr Anja Schwenzer, who led the project. “We decided to see if it could be citrullinated and, if so, whether it was a target for the autoantibodies that attack the body in rheumatoid arthritis. That might also indicate whether it could be used in tests to indicate the disease.

“When we looked at results from more than 2,000 patients we found that testing for antibodies that target citrullinated tenascin-C (cTNC) could diagnose rheumatoid arthritis in around 50% of cases, including some cases not identified by CCP. It also has a very low rate of false positives – it is 98% accurate at ruling out rheumatoid arthritis.”

Prof Kim Midwood, who is also involved in the work, comments:

“What is particularly exciting is that when we looked at samples taken from people before their arthritis began, we could see these antibodies to cTNC up to 16 years before the disease occurred – on average the antibodies could be found seven years before the disease appeared.

“This discovery therefore gives us an additional test that can be used to increase the accuracy of the CCP assay and that can predict rheumatoid, enabling us to monitor people and spot the disease early. This early detection is key because early treatment is more effective.”