Anti-CCP optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for Anti-CCP:
- Optimal 0 – 20 U/mL (0 – 20 AU/mL); sufficient 20 – 40 U/mL (20 – 40 AU/mL); out of range below 0 or above 40 U/mL.
Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| U/mL | 0 – 20 | 20 – 40 | below 0 or above 40 |
| AU/mL | 0 – 20 | 20 – 40 | below 0 or above 40 |
What the evidence says
The 20 U/mL edge is the cut-off the great majority of assays are calibrated to, not a guideline figure; on that scale laboratories such as ARUP report 20 to 39 as weak positive and 40 and above as moderate to strong positive, which is where the acceptable band ends. ACR/EULAR score this marker against the issuing laboratory's own upper limit, so read a borderline value against the interval on the report. Specificity for rheumatoid arthritis is high, around 95%, and antibodies can appear years before joint symptoms do.
Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.
Sources
- Cyclic Citrullinated Peptide Antibody, IgG and IgA — ARUP Laboratories, 2026 · Laboratory / reference-interval source19 Units or less is negative, 20 to 39 weak positive, 40 to 59 moderate positive, 60 or greater strong positive. Sera's optimal band ends at the negative cut-off and its acceptable band at the end of weak positive.
- Rheumatoid Arthritis Classification Criteria — American College of Rheumatology / European League Against Rheumatism, 2010 · Professional societyScores anti-CCP and rheumatoid factor against the issuing assay's own upper limit of normal, separating low-positive (up to three times that limit) from high-positive. Sera's optimal/acceptable split mirrors that tiering; the criteria set no absolute cut-off in U/mL, which is why the marker is flagged assay-dependent.
What Anti-CCP (Cyclic Citrullinated Peptide) measures
An antibody against citrullinated proteins, and the most specific blood marker for rheumatoid arthritis.
Specificity is around 95%, so a clear positive alongside joint symptoms carries far more weight than rheumatoid factor does. It can appear years before symptoms, which is why a positive in someone with vague joint pain is worth acting on. The cut-off differs between assays — read a borderline value against the interval on the report.