Diagnosing Rheumatoid Arthritis: Rheumatoid Factor & Anti-CCP
Rheumatoid factor (RF) is a reactive IgM autoantibody which is positive in approximately 80% of patients within one year of presentation of rheumatoid arthritis (RA), but in only 30% at the onset of arthritis.
Anti-CCP (cyclic citrullinated peptide) is an autoantibody which appears early in the course of RA. When it is detected in a patient’s blood, there is a high likelihood that the patient has RA.
Anti-CCP has higher sensitivity and specificity than RF for diagnosis of RA.
| RF | Anti-CCP |
| May be negative in early RA | Occurs years before clinical onset of arthritis |
| Lower specificity (18.0%)* | Higher specificity (94.5%)* |
| Lower sensitivity (69.7%)* | Higher sensitivity (74.0%)* |
| Not a marker for disease progression | Indicates more aggressive and destructive form of disease and marker for disease progression |
| Present in 5% normal individuals | Elevated levels not seen in normal individuals |
*Saureland U, Becker H, Seidel M, Schotte H, Willeke P, Schorat A et al. Clinical utility of the anti-CCP assay: experience with 700 patients. Ann N Y Acad Sci. 2005 Jun; 1050:314-8.
Suburban Diagnostics performed a study using data from patients tested for RF and Anti-CCP together (for the diagnosis of RA) over the past 3 years.
- 13% tested positive for RF
- 18.5% tested positive for Anti-CCP
Anti-CCP is expected to be positive in early cases of RA even before the clinical presentation but RF is usually negative in the early phases of rheumatoid arthritis.
| Results | Interpretation | Percentage of cases |
| Both positive | RA present | 11.3% |
| Anti-CCP positive, RF negative | Early stages of RA | 7.3% |
| Anti-CCP negative, RF positive | Unlikely to be RA; Clinical evaluation necessary | 1.7% |
| Both negative | Highly unlikely to be RA; Clinical evaluation necessary to rule our SERONEGATIVE RA | 79.7% |
There is an entity known as SERONEGATIVE RA, where RF & Anti-CCP are negative. In these cases, clinical correlation with inflammatory markers, symptoms and medical history will be required for diagnosis.
RA & Anti-CCP results were:
- More likely to be positive in females
- More likely to be negative in males
In our study, no specific correlation is seen between the age group and positivity of RA and Anti-CCP. Hence, as a conclusion for diagnosis of RA we can state that testing for both RF & Anti-CCP is ideal. If testing for only one marker, then Anti-CCP is most recommended.
#unburdenhealthcare with us.
