The ACR/EULAR classification criteria for rheumatoid arthritis is a clinical calculator developed jointly by the American College of Rheumatology (ACR) and the European League Against Rheumatism (EULAR). This calculator is used to classify patients with rheumatoid arthritis, a chronic inflammatory disorder affecting the joints. 

The ACR/EULAR criteria are applied to patients who have at least one joint with definite clinical synovitis (swelling) not better explained by another disease. The criteria are based on the weighted sum of four domains: joint involvement, serology (including rheumatoid factor and anti-citrullinated protein antibody status), acute-phase reactants (C-reactive protein level and erythrocyte sedimentation rate), and duration of symptoms. 

The clinical utility of this calculator is to aid in the diagnosis of rheumatoid arthritis, particularly in its early stages, and to differentiate it from other forms of arthritis or joint diseases. It is not intended to be used as the sole criteria for diagnosing rheumatoid arthritis, but rather as a tool to support clinical judgment. 

Exclusion criteria for the use of this calculator include patients with conditions that could better explain the synovitis, such as lupus, psoriatic arthritis, or g

ACR/EULAR classification criteria for rheumatoid arthritis

# Criteria
 ## Joint involvement
A. 1 large joint (+0)
B. 2-10 large joints (+1)
C. 1-3 small joints (+2)
D. 4-10 small joints (+3)
E. > 10 joints including at least 1 small joint (+5)
## Serology
F. Negative rheumatoid factor and negative anti-cyclic citrullinated peptide antibody (+0)
G. Low-positive rheumatoid factor and negative anti-cyclic citrullinated peptide antibody (+2)
H. High-positive rheumatoid factor or positive anti-cyclic citrullinated peptide antibody (+3)
## Acute phase reactants
I. Normal C-reactive protein and erythrocyte sedimentation rate (+0)
K. Abnormal C-reactive protein or erythrocyte sedimentation rate (+1)
## Duration of symptoms
L. < 6 weeks (+0)
M. >= 6 weeks (+1)

# Conditions
- score >= 6
- true
- score == 0