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.