Relationship of rheumatoid factor to lung diffusion capacity in smoking and non-smoking patients with rheumatoid arthritis.

We studied the relationship of serum rheumatoid factor (RF) and certain other variables to lung diffusion capacity for carbon monoxide (DLCO) in patients with rheumatoid arthritis (RA). In non-smoking patients none of the examined variables correlated significantly to DLCO whereas in smokers RF showed a significant (p < 0.01) negative correlation in this respect. These results indicate that smoking in connection with RF may contribute to reduced DLCO in RA patients.