The research, led by the University of Warwick in the UK, is published in the journal Scientific Reports.
The authors found that testing for citrullinated proteins (CPs) in the blood could lead to osteoarthritis (OA) being diagnosed years before physical symptoms emerge.
They also found that CPs may serve as a reliable way to detect early-stage rheumatoid arthritis (RA). 
Lead researcher Dr. Naila Rabbani, reader of experimental systems biology at Warwick, says:
“This is a remarkable and unexpected finding. It could help bring early-stage and appropriate treatment for arthritis, which gives the best chance of effective treatment.”
Dr. Rabbani and colleagues note that while there are established biomarker tests for early-stage RA, there are none for OA and suggest their findings could lead to a test for both that also distinguishes between the two.