18th January 2024

Classification criteria in RA

2010 American College of Rheumatology (ACR)/ European League Against Rheumatism (EULAR) Classification Criteria

The following criteria are required to be met in order to be classified as having a definite RA diagnosis:

• Presence of synovitis in at least 1 joint
• Absence of an alternative diagnosis which better explains the synovitis
• Total score of at least 6 (out of a maximum of 10) from the individual scores in the 4 domains, which include:
  • Number and site of joints involved- greater number of points for smaller joints affected.
  • Serological abnormality (RF or anti-CCP positive)
  • Elevated CRP or ESR
  • Symptom duration at least 6 weeks

Disease Activity Score (DAS)

The DAS is used to clinically measure disease activity in patients with RA and is particularly useful for targeting and objectively measuring response to treatment. It objectively measures tenderness and swelling of the shoulder, elbow, wrist, knee, MTP and PIP joints and includes a subjective measure of the patient’s general health based on a visual analogue scale.

The DAS 28 score considers the following four variables:

• The number of swollen joints (0-28)
• The number of tender joints (0-28)
• ESR or CRP
• Visual analogue scale (VAS)disease activity (0-100mm)

The formula used to calculate the score is: (0.56*√ (tender joints) +0.28*√ (swollen joints) +0.70*Ln(ESR/CRP) +0.014*VAS)

An overall score is calculated out of 10, with a score > 5.1 indicating high disease activity and a score of <3.2 indicating low disease activity. NICE recommends using the DAS as one of the criteria for starting biological therapy.