Rheumatoid arthritis (RA) has been traditionally defined as a chronic inflammatory auto-immune disease characterized by joint swelling and tenderness with a potential for joint damage and destruction. And for quite some time, the diagnosis had been primarily based on ARA Classification Criteria first published in 1987. Based on this criteria set, a patient can be said to have RA is s/he satisfies four of the following seven criteria:
Morning stiffness lasting at least 1 hour before maximal improvement
Arthritis involving at least 3 of 14 joint areas observed by a physician
Arthritis involving the hand joints (MCPs, PIPs or wrists)
Symmetric involvement of several joint areas
Positive Rheumatoid Factor (RF)
Radiographic changes typical of RA
* Criteria 1-4 should be present for AT LEAST 6 WEEKS.
This criteria is well accepted as the benchmark for disease definition but it is significantly limited as it was originally derived to discriminate rather than diagnose patients with established RA against those with other rheumatic conditions. Another limitation is its inability to identify patients with early disease who may potentially benefit from early effective intervention.
Success of RA management has greatly improved over the last couple of years with the optimal use of disease modifying anti-rheumatic drugs (DMARDs) and the introduction of new biologic agents. More so, it has been recognized that early intervention improves disease outcome and reduces accrual of joint damage and disability. The need, therefore, to identify those with early disease at which point joint damage can be prevented (rather than minimized) became the ideal. Unfortunately, clinical trials exploring interventions aimed at preventing RA joint damage has been hampered by the lack of validated criteria to identify patients with early disease.
Thus the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) collaborated to develop a new approach to RA classification. Again, despite the original intention for producing the new criteria, the ACR/ EULAR Collaboration is for classification of patients with definite RA and not for patients with “early” RA.
The following 2010 ACR/ EULAR Classification Criteria can only be applied if the following two prerequisites are met: (1) evidence of currently active synovitis (swelling) of at least one joint; and, (2) the observed synovitis cannot be better explained by another diagnosis (i.e. SLE, psoriatic arthritis and gout).
A score-based approach had been adopted in the new criteria and a score of at least 6 is needed to classify a patient as having definite RA. Here are some definitions of the terms used above:
- LARGE joints – refers to the shoulders, elbows, hips, knees and ankles.
SMALL joints – refers to the MCPs, PIPs, 2nd to 5th MTPs, thumb IP and wrists. The DIPs, 1st CMC and 1st MTP are excluded from the joint assessment.
ACPA – anti-citrullinated protein antibodies – which have been shown to be a better diagnostic tool than rheumatoid factor. Tests for Anti-cyclic citrullinated protein (Anti-CCP) Antibodies, a form of ACPA, is available at SLMC, PGH and Hi-Precision Diagnostic in the Philippines.
Interpretation of Titers for RF and ACPA:
NEGATIVE – test result is below the upper limit of normal (ULN)
LOW POSITIVE – test result is above ULN but less than three times the ULN. If only a QUALITATIVE assay for RF is done, a positive RF is scored as a LOW-POSITIVE TITER for RF.
HIGH POSITIVE – test result is more than three times the ULN.
An interesting note in the paper introducing the new classification criteria is the absence of radiographic evidence of erosions on hand radiographs. Their explanation is simple, the criteria was developed to enable diagnosis and treatment earlier in the course of the disease so as to prevent disease complications. Thus, those with joint erosions characteristic of RA were deemed to have prima facie evidence of the disease and can already be classified as having such.
The above criteria have so far been validated in three cohorts of patients in the Netherlands, UK and Canada. It would be interesting to find out how these criteria perform in our patients with RA and in those who were previously diagnosed as having undifferentiated CTD or undifferentiated inflammatory arthritis.
Aletaha D, Neogi T, Silman A, et al. 2010 Rheumatoid Arthritis Classification Criteria: an ACR/ EULAR collaborative initiative. Ann Rheum Dis 2010; 69: 1580-88.