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Diagnosing Rheumatoid Arthritis: Rheumatoid Factor & Anti-CCP

  • October 12,2021
  • 5 Min Read
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.

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