New criteria for rheumatoid arthritis (RA), published in the Annals of Rheumatic Diseases, could prevent thousands of people from developing disabling late stage disease, by redefining how RA should be classified.

Rheumatoid arthritis is a progressive autoimmune inflammatory disease, primarily of the joints. If untreated, it leads to damage of bone and cartilage, joint deformities and disability. Around 350,000 people in the UK are living with RA, which affects around three times as many women as men.

Late stage rheumatoid arthritis has also been linked to a higher risk of serious heart disease and premature death.

The new criteria, which were developed jointly in three phases by the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR), are based on data from real patients and clinical consensus.

They replace existing ACR criteria published in 1987, which focused on established, rather than early indicators of disease. The new 2010 criteria focus on early diagnosis and treatment, which has become increasingly important with the advent of more effective drug treatments over the past decade.

If picked up early, synthetic and biological disease modifying antirheumatic drugs (DMARDs) can prevent the destructive and disabling joint damage, which is a hallmark of late stage RA.

The new criteria aim to recognise RA early on in its development, in a bid to target preventive treatment more effectively and channel into clinical trials patients who could benefit from promising new therapies for the disease.

The new criteria classify "definite RA" as:

* The confirmed presence of synovitis - inflammation of the synovial membrane that lines the joint - in at least one joint

* The absence of an alternative diagnosis to explain the synovitis, for example gout or arthritis triggered by infection (reactive arthritis)

* A combined score of 6 or more from each of the following four domains:

-number and sites of affected joints

-blood tests results (for autoantibodies indicative of RA)

-evidence of an increase in inflammatory proteins (known as the acute phase response)

-how long symptoms have lasted

"The new criteria redefine RA, reflecting our collective hope that in the future, RA will no longer be characterised by erosive joint disease and persistence of symptoms, although these characteristics will continue to define established or longstanding untreated disease," write the working party authors.

The importance of treating RA promptly has been recognised both by NICE (management guidelines for treatment of RA) and the national Audit Office (management of RA).