Anti-citrullinated peptide antibodies in the serum of heavy smokers without rheumatoid arthritis. A differential effect of chronic obstructive pulmonary disease?

The objective of this study is to analyse the frequency and levels of anti-citrullinated peptide/protein antibodies (ACPA) in the serum of non-rheumatoid arthritis (RA) heavy smokers with and without chronic obstructive pulmonary disease (COPD) and compare them with healthy never smokers and patients with RA. Serum samples of 110 heavy smokers without RA, 209 healthy never smokers and 134 patients with RA were tested for ACPA using a commercial anti-cyclic citrullinated peptide antibodies (CCP2) test and a homemade chimeric fibrin/filaggrin citrullinated synthetic peptide (anti-CFFCP) ELISA test. The frequency of positive results and autoantibody levels were compared between groups. The prevalence of the two types of ACPA was slightly higher in heavy smokers than in never smokers, although the difference was not significant, and significantly lower than in RA patients. The highest prevalence of positive ACPA in heavy smokers was found in subjects with COPD (7.4% of positive anti-CFFCP in patients with COPD in comparison with 2.4% in never smokers: OR 3.26; 95% CI 0.85-12.6, p = 0.089). Mean serum levels of ACPA in heavy smokers were not significantly different from those of never smokers. Heavy smokers with COPD had significantly higher levels of anti-CFFCP than those without COPD, although almost all patients had serum levels below the cut-off values. The prevalence of ACPA in heavy smokers without RA is low, but seems to be higher in heavy smokers with COPD. Larger studies are necessary to confirm these findings and determine the relationship between ACPA and lung disease.