How to Order Anti-CCP IgG Assay
Order the anti-cyclic citrullinated peptide (anti-CCP) IgG antibody test as a serum test, specifically requesting the IgG isotype, using an automated second or third-generation assay when available.
When to Order Anti-CCP IgG
The primary indication for ordering anti-CCP testing depends on your clinical context:
For Suspected Rheumatoid Arthritis
- Order anti-CCP when rheumatoid factor (RF) is negative and you still suspect RA with persistent synovitis, especially if considering combination DMARD therapy 1
- Test for RF first in patients with suspected RA who have synovitis 1
- Anti-CCP should be part of the initial workup alongside RF, as both provide complementary diagnostic information 2
For Immune Checkpoint Inhibitor Patients
- Include anti-CCP in the autoimmune panel (along with ANA, RF, ESR, and CRP) when evaluating Grade 1 or higher immune-related rheumatologic adverse events 3
For Bronchiectasis Evaluation
- Consider anti-CCP testing when evaluating for rheumatoid arthritis as an underlying cause of bronchiectasis, though recognize that only 12% of RF-positive bronchiectasis patients will have strongly positive anti-CCP 4
Test Specifications
Assay Selection
Prioritize automated second or third-generation anti-CCP assays over manual ELISA methods when available 5. Automated platforms (such as Architect i2000SR, ImmunoCAP 250, or Cobas e 411) offer:
- Better correlation with clinical RA diagnosis
- Higher reproducibility with correlation coefficients of 0.615-0.861 between platforms 6
- Comparable diagnostic sensitivities (90.6-93.8%) and specificities (85.5-86.8%) 6
Isotype to Order
Request IgG anti-CCP specifically as the standard test 2. While combined IgG/IgA assays exist, IgG remains the validated standard for diagnosis and prognosis.
Interpreting Results
Diagnostic Performance
- Specificity: 96% - highly specific for RA 7
- Sensitivity: 60-66% - moderate sensitivity, meaning negative results don't exclude RA 2, 8
- Anti-CCP has higher specificity (90%) compared to RF (70%) 2
Clinical Significance of Positive Results
A positive anti-CCP indicates:
- 43 times higher likelihood of having RA versus not having RA (diagnostic odds ratio 43.05) 8
- Strong association with radiological defects and bone erosions 9
- Increased risk of persistent, erosive disease requiring early aggressive therapy 2
- Positive predictive value of 86.7% for RA diagnosis 7
Important Caveats
- Negative anti-CCP does not exclude RA - 36.6% false-negative rate in early disease 7
- Anti-CCP can be positive in other conditions (3.9% false-positive rate), though this is rare 7
- Cutoff values matter: Standard manufacturer cutoffs may need adjustment based on the differential diagnosis being considered 10
Timing and Follow-Up
- Order at baseline evaluation when RA is suspected 11
- Repeat testing is generally not recommended for monitoring disease activity, as anti-CCP levels don't reliably track with disease activity scores
- The test is most valuable for initial diagnosis and prognostication, particularly for predicting erosive disease
Common Pitfalls to Avoid
- Don't skip RF testing - Order RF first or simultaneously, not anti-CCP alone 1
- Don't use anti-CCP as a screening test in low-probability patients - reserve for those with clinical synovitis
- Don't assume negative anti-CCP rules out RA - clinical diagnosis remains paramount with 36.6% false-negative rate 7
- Don't order anti-CCP for disease activity monitoring - it's a diagnostic/prognostic tool, not a disease activity marker