Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (882 page)

   Antibodies to citrullinated proteins are markers of RA, especially for early diagnosis of the disease. In some cases, these antibodies may be detected many years before the onset of the first symptoms. Other names: CCP-IgG, citrullinated antibody, anticitrullinated antibody, anticitrullinated protein antibody (ACPA).

   
Normal range:

   Less than 20 U: negative

   20–39 U: weak positive

   40–59 U: moderate positive

   ≥60 U: strong positive

   Use

   Evaluating patients suspected of having RA. The 2010 American College of Rheumatology guidelines recommend performing at least one serologic test (RF or CCP-IgG) and one acute-phase response measure (ESR or CRP) to classify a patient as having or not having definite RA in addition to a history of symptom duration and a thorough joint evaluation.

   Differentiating RA from other connective tissue diseases that may present with arthritis and may be positive for RF, such as HCV-associated cryoglobulinemia, undifferentiated polyarthritis, and Sjögren syndrome.

   Differential diagnosis of early polyarthritis.

   Interpretation

   Increased in RA (a positive result for CCP antibodies indicates a high likelihood of RA).

   Limitations