For a study, researchers sought to look for autoantibodies to cyclic citrullinated synthetic peptides (ACPAs) in the sputum of people who had rheumatoid arthritis (RA) for a long time. The cross-sectional study included 19 patients with RA and 16 age- and gender-matched control volunteers. All of them had comprehensive pulmonary function tests and induced sputum. Antibodies to citrullinated (CitP) and norleucine-containing (NorP) peptides were detected in the sputum of patients with RA and control participants, as well as in the serum of RA patients, using an enzyme-linked immunosorbent test.

The following features were found in RA patients: a mean disease duration of 12 years, a Disease Activity Score for 28 joints of 3.44, and a Sharp–van der Heijde score of 57.5. ACPA titers in the serum of ten of the 19 RA patients were high. ACPAs were detected in the sputum of four of the seropositive (40%) RA patients, none of the seronegative RA patients, and only one of the control participants. The ratio of reactivity with CitP and NorP peptides in RA sputum to control sputum was substantially greater (1.33 +1.2 vs. 0.64+ 0.14, P=0.02). Sputum ACPAs and age, serum ACPAs, sputum anti-NorP, serum anti-CitP/NorP reactivity ratio, and the number of neutrophils and lymphocytes in the sputum all showed a positive connection. There was no statistically significant relationship between sputum ACPAs and disease severity, smoking history, pulmonary function testing, or RA medication. Antiicitrullinated protein/peptide antibodies could be found in RA patients’ sputum and were linked to their presence in the serum.