The presence of IgA class antibodies against cyclic citrullinated peptides (IgA anti-CCPs) identifies patients with early rheumatoid arthritis (RA) who are likely to develop severe disease, report researchers.
IgG class anti-CCPs have drastically changed routine serological testing for RA, say Anna Svärd (Falu Hospital, Falun, Sweden) and co-workers.
They are not only highly specific diagnostic markers, but they also predict disease outcome and likely progression.
For the present study, Svärd and team compared IgG anti-CCPs with IgA anti-CCPs in 228 patients from the Swedish TIRA Study, who had developed RA in the 12 months prior to becoming involved with the current study.
Testing of sera at the start of the study showed that 29.0% of patients carried IgA anti-CCP antibodies. Furthermore, all participants positive for IgA anti-CCP also carried IgG anti-CCP antibodies at higher levels than those negative for IgA anti-CCPs.
Of greater note, the presence of IgA anti-CCP antibodies was significantly predictive of disease activity over the 3-year study follow-up period. Importantly, this relationship was independent of smoking status - a major RA risk factor in certain patients.
Bringing their findings together, the investigators conclude: "IgA anti-CCP antibody analysis does not appear to add a diagnostic benefit to IgG anti-CCP alone, but the presence of IgA class antibodies may predict a more severe disease course in early RA."
Conceding that the prognostic properties of IgA anti-CCP could be related to the presence of IgG anti-CCP antibodies the researchers conclude, in the journal Arthritis Research and Therapy: "Further studies are justified to shed more light on this question."