Undifferentiated polyarthritis : is it a hidden Form of RA? The value of anticyclic citrullinated peptide antibodies as a diagnostic and prognostic marker for RA

Abstract EN

Objective : the study was undertaken to assess the value of anti-cyclic citrullinated peptide antibodies (anti-CCP) in comparison to anti-per nuclear factor (APF) and IgM rheumatoid factor (IgM RF) in the early diagnosis of rheumatoid arthritis (RA) in patients with undifferentiated polyarthritis (UPA).

Methodology : serum samples of sixty patients with UPA (not fulfilling any of the ACR criteria for the diagnosis of any of the connective tissue diseases) and of other twenty age and sex matched healthy volunteers act as a control group was tested for IgM RF, APF and anti-CCP antibodies at first visit.

Follow-up and reassessment of all patients was done monthly till the end of the study after one year.

Measurement of APF was done by indirect immunofluorescence (IIF) and anti-CCP was done by enzyme linked immunosorbent assay (ELISA).

Results : Forty two (70 %) out of 60 UPA patients met the revised criteria of diagnosis of RA after one year of follow-up.

A positive anti-CCP test was highly specific for RA (specificity 88.8 %) being found in 30 (71.5 %) out of 42 RA patients and its sensitivity was (71.4 %).

IgM RF had the highest sensitivity (76 %) and it was less specific for RA (66.6 %) while the specificity and the sensitivity of APF were 77.7 % and 52.38 %, respectively.

There was a highly significant association between anti-CCP antibodies positive RA patients and high disease activity score as well as disease severity score (p < 0.001) while there was significant association between IgM RF and APF positive RA patients separately and high disease activity score (p < 0.02 & 0.01, respectively) as well as disease severity score (p < 0.05 & 0.01, respectively).

Conclusion: Anti-CCP antibody is a highly specific serologic marker for RA and its determination is of value in the diagnosis of early cases of RA.

Furthermore, anti-CCP may have prognostic significance because of their association with more severe and active form of RA.