Testing for antibodies that target citrullinated tenascin-C (cTNC) could diagnose RA in around 50% of cases, including some cases not identified by current best tests. It also has a very low rate of false positives – 98% accurate at ruling out RA.
When inflammation occurs in the body, some proteins are altered in a process called citrullination. These altered forms can cause an autoimmune attack and RA. For that reason, tests that spot antibodies to citrullinated proteins are already used to diagnose the disease. While tests for individual proteins usually have a relatively low diagnostic sensitivity, a more general test called CCP, that detects synthetic citrullinated peptides, identifies a lot more RA cases.
Dr Anja Schwenzer said: ‘We knew that tenascin-C is found at high levels in the joints of people with RA. 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 RA. That might also indicate whether it could be used in tests to indicate the disease. ‘When we looked at results from more than 2000 patients we found that testing for antibodies that target citrullinated tenascin-C (cTNC) could diagnose RA 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 RA.’
The Kennedy Institute’s Professor Kim Midwood said: ‘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 7 years before the disease appeared. This early detection is key because early treatment is more effective.’ This could have great potential to help patients with rheumatoid arthritis get the right treatment early to keep this painful and debilitating condition under control.’ https://www.ox.ac.uk/news/2015-12-10-blood-test-could-predict-arthritis-risk
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