Definitions of chronic inflammatory rheumatisms (CIR): rheumatoid arthritis according to the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria [37]; spondyloarthritis according the European Spondyloarthropathy Study Group (ESSG) Classification [38]; undifferentiated polyarthritis (own study criteria).

* Joint involvement refers to any swollen or tender joint on examination, which may be confirmed by imaging evidence of synovitis. DIP, first CMC, and first MTP are excluded from assessment. Categories of joint distribution are classified according to the location and number of involved joints, with placement into the highest category possible based on the pattern of joint involvement. “Large joints” refers to shoulders, elbows, hips, knees, and ankles. “Small joints” refers to the MC, PIP, second through fifth MTP, thumb IP joints, and wrists.
** In this category, at least 1 of the involved joints must be a small joint; the other joints can include any combination of large and additional small joints, as well as other joints not specifically listed (e.g., temporomandibular, acromioclavicular, sternoclavicular…).
*** Negative refers to international unit (IU) values that are less than or equal to the upper limit of normal (ULN) for the laboratory and assay; low-positive refers to IU values that are higher than the ULN but ≤ 3 times the ULN for the laboratory and assay; high-positive refers to IU values that are > 3 times the ULN for the laboratory and assay. Where RF information is only available as positive or negative, a positive result should be scored as low-positive for RF.
****Normal/abnormal is determined by local laboratory standards.
IP = interphalageal;
PIP = proximal interphalangeal;
DIP = distal interphalangeal;
CMC = carpometacarpal;
MCP = metacarpophalangeal;
MTP = metatarsophalangeal;
CRP = C-reactive protein;
ESR = erythrocyte sedimentation rate;
ACPA = anti-citrullinated protein antibody.
Definitions of chronic inflammatory rheumatisms (CIR): rheumatoid arthritis according to the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria [37]; spondyloarthritis according the European Spondyloarthropathy Study Group (ESSG) Classification [38]; undifferentiated polyarthritis (own study criteria).