By Pat Anson, Editor

British researchers are close to developing a blood test that would detect osteoarthritis in its early stages, a development that could lead to diagnosis and treatment of the disease years before joint damage occurs.

Osteoarthritis is a progressive joint disorder caused by painful inflammation of soft tissue, which leads to thinning of cartilage and joint damage in the knees, hips, fingers and spine. The World Health Organization estimates that about 10% of men and 18% of women over age 60 have osteoarthritis.

Researchers at the University of Warwick’s Medical School have identified a biomarker linked to both rheumatoid and osteoarthritis. Diagnostic blood tests already exist for rheumatoid arthritis (RA), but the newly identified biomarker could lead to one which can diagnose both RA and osteoarthritis (OA).

“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,” said lead researcher  Naila Rabbani, PhD.

“This discovery raises the potential of a blood test that can help diagnose both RA and OA several years before the onset of physical symptoms."

Rheumatoid arthritis is a chronic autoimmune disease in which the body’s own defenses attack joint tissues, causing swelling, inflammation and bone erosion. About 1% of adults worldwide suffer from RA.

Rabbani’s research focused on citrullinated proteins (CPs), a biomarker suspected to be present in the blood of people with early stage rheumatoid arthritis. It had previously been established that patients with RA have antibodies to CPs, but it was not thought that this was the same for those with OA.

However, the Warwick researchers found for the first time increased CPs levels in both early-stage OA and RA.

They then produced an algorithm of three biomarkers; CPs, anti-CP antibodies, and a bone-derived substance called hydroxyproline.

Using the algorithm the researchers found that with a single test they could potentially detect and discriminate between the two types of arthritis in their early stages, before joint damage has occurred. The test correctly identified 73% of the people with eary OA and 57% of the people with early RA.

“It has been long established that the autoimmunity of early-stage RA leads to antibodies to CPs, but the autoimmunity, and hence antibodies, are absent in early-stage OA. Using this knowledge and applying the algorithm of biomarkers we developed provides the basis to discriminate between these two major types of arthritis at an early stage,” said Rabbani.

“Detection of early stage-OA made the study very promising and we would have been satisfied with this only – but beyond this we also found we could detect and discriminate early-stage RA and other inflammatory joint diseases at the same.

The research is published online in Nature Scientific Reports.