From the Guidelines
Cyclic citrullinated peptide (CCP) IgG antibody is a highly specific blood test used to diagnose rheumatoid arthritis (RA), with a positive result strongly suggesting RA, while a negative result doesn't rule it out. To perform the test:
- Order a "CCP antibody" or "anti-CCP" blood test
- Draw a blood sample from the patient
- Send to the lab for analysis
- Results are typically reported as positive or negative, with a numerical value Interpretation:
- Positive: >20 units/mL
- Negative: <20 units/mL The test is highly specific (95-98%) for RA, meaning a positive result is very likely to indicate RA, as noted in studies such as 1 and 1. However, sensitivity is lower (60-75%), so a negative result doesn't exclude RA. CCP antibodies often appear years before clinical symptoms, making this test valuable for early diagnosis, as discussed in 1. It's also useful for predicting disease severity and potential joint damage. This test is particularly helpful when rheumatoid factor (RF) is negative, as up to 40% of RF-negative RA patients may be CCP-positive, highlighting the importance of considering both tests for a comprehensive evaluation, as suggested in 1. Key considerations in the interpretation and application of CCP antibody tests include their role in assessing disease activity and prognosis, as outlined in 1 and 1, which provide guidance on the management of rheumatoid arthritis.
From the Research
Definition and Characteristics of Cyclic Citrullinated Peptide (CCP) IgG Antibodies
- CCP IgG antibodies are specific diagnostic markers of rheumatoid arthritis (RA) 2
- They are a collection of anti-citrullinated protein antibodies (ACPA) and contain overlapping and non-overlapping reactivities 3
- The presence of anti-CCP antibodies is significantly associated with the presence of HLA-DRB1 shared epitope (SE) alleles 2
Diagnostic Performance of CCP IgG Antibodies
- CCP IgG antibodies have a high specificity in the diagnosis of RA, with a diagnostic specificity of 95.8% 2
- The combination of anti-CCP antibodies with IgA RF or the combination of the three serological markers (anti-CCP, IgM RF, and IgA RF) increases the specificity of the diagnosis of RA 4
- Anti-CCP antibodies can be present in patients with hepatitis C virus infection, but at lower levels than in patients with RA 5
Prognostic Value of CCP IgG Antibodies
- The presence of anti-CCP antibodies is associated with clinical signs of disease severity, such as functional disability, presence of erosions, and absence of clinical remission 4
- The titer of anti-CCP antibodies predicts the time to RA onset in patients with undifferentiated arthritis, with higher titers associated with a shorter time to diagnosis 6
- The presence of anti-CCP antibodies at both low and high titer is significantly associated with RA development in subjects with recent onset undifferentiated arthritis 6