Arthritis - Rheumatoid
The two important factors to consider when diagnosing RA are 1) whether inflammation is present, and 2) whether an autoimmune response is occurring. Inflammation can be measured with a variety of blood tests including hs-CRP (measures inflammation quantitatively) and an erythrocyte sedimentation rate (ESR) test (measures inflammation functionally) (St. Clair 2004).
To help determine if an autoimmune reaction is taking place, doctors often assess the levels of two proteins: rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA), sometimes referred to as anti-cyclic citrullinated protein (anti-CCP). Both RF and ACPA are autoantibodies involved in the immune attack against self-tissue in RA.
Table 1. Criteria for a definitive diagnosis of rheumatoid arthritis.> A definitive diagnosis requires confirming synovitis due to RA in at least one joint. Additionally, a total score ≥ 6 by adding the individual criterion scores below (Aletaha 2010; Pietschmann 2011).
|Number and site of joints involved||0-5||Add one point for each joint involved.||"Involved" means a joint is inflamed.||Physical exam, patient report, and/or imaging of the joint|
Serologic abnormality(abnormal blood test results)
0 = Normal
1 = Abnormalities are present at low levels
2 = Abnormalities are present at high levels
|The presence (high or low levels) or absence of either RF or ACPA; high score indicative of autoimmunity.||Blood test analyzed by laboratory|
|Elevated Acute-Phase Response||0-1||
0 = Test is negative
1 = Test is abnormal
|"Abnormal" means elevated CRP or high ESR; high scores indicate inflammation||Blood test analyzed by laboratory|
0 = Symptoms have persisted for less than 6 weeks
1 = Symptoms have persisted for 6 weeks or longer
|Symptoms that do not resolve within 6 weeks are indicative of RA.||Monitoring by doctor/patient report|