Abstract:
To establish the diagnostic utility of the anticyclic-
citrullinated peptide antibody (aCCP) test in Black
South Africans with early rheumatoid arthritis (RA). A
cross-sectional study comparing the rheumatoid factor (RF)
and aCCP status in RA patients and a control group
consisting of healthy subjects, and patients with systemic
lupus erythematosus (SLE) and scleroderma. The sensitivity,
specificity, positive (PPV) and negative predictive values of
the aCCP test alone were 82.5%, 84.9%, 87.6% and 79%
versus 81.7%, 90.7%, 92.5% and 78% for RF alone. The best
specificity (95.3) and PPV (95.8%) was observed when both
aCCP and RF tests were positive. Patients with erosive
disease had a significantly higher mean RF titre compared
with those with non-erosive disease (p=0.007). There was
a trend towards an association of smoking (OR=4.1, 95%
CI=0.9–18.6) and functional disability (p=0.07) with
RF-positive status. No similar clinical associations were
observed with aCCP. Almost a third of SLE patients were
aCCP positive. Despite the best specificity and PPVobserved
when both the aCCP and RF tests were positive, our findings
suggest that testing for aCCP is only cost-effective in the
RF-negative patient in whom there is a strong clinical
suspicion of RA.
