Svard A et al. - Anti-cyclic citrullinated peptides (CCP) antibodies of IgA class were found in about 1/3 of patients with recent-onset RA, all of whom also had IgG anti-CCP antibodies. The occurrence of IgA class antibodies was associated with smoking, and IgA-positive patients had a more severe disease course over three years compared to IgA-negative cases. Methods
Study to assess whether IgA class Abs against anti-CCP in recent-onset RA adds diagnostic and/or prognostic information to IgG anti-CCP analysis
Serum samples from 228 pts
Sera from 72 of these pts were also available at the 3-yr f/u
Disease activity and functional ability measures were registered at inclusion and regular f/u during 3 yrs
An IgA anti-CCP antibody assay was developed replacing the detection antibody by an anti-human-IgA antibody
A positive IgA anti-CCP test was defined by the 99th percentile among healthy blood donors
Results
At baseline, a positive IgA anti-CCP test was observed in 29% of the patient sera
All tested positive for IgG anti-CCP at a higher average level than sera containing IgG anti-CCP Abs alone
The IgA anti-CCP positive pts had higher disease activity over time vs IgA anti-CCP negative pts
Also after considering IgG anti-CCP level, the disease activity was higher in the IgA anti-CCP positive cases
The proportion of IgA anti-CCP positive pts was larger among smokers vs non-smokers
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