To study signs of obstructive airway disease (OAD) in patients with primary Sjögren's syndrome (pSS) using the forced oscillation technique (FOT).
Thirty-seven female pSS patients (median age 64, range 38-77 years) without previous physician-diagnosed OAD, participating in a longitudinal follow-up study of pulmonary function, and 74 female population-based controls (median age 64, range 47-77 years), also without physician-diagnosed OAD, and matched with regard to age, height, weight, and tobacco consumption, were included in the study. The pSS patients and controls were studied by the FOT, evaluating resistance and reactance of the respiratory system.
pSS patients had significantly increased resistances at 5-25 Hz, decreased reactance at 10-35 Hz, and an increased resonant frequency (Fres) in comparison with controls. Resistance was correlated negatively and reactance positively to the vital capacity (VC), the forced expiratory volume in 1 s (FEV1), and the diffusing capacity for carbon monoxide (DLCO). Compared with controls, pSS patients with (n = 14) and without OAD (n = 21), as determined by spirometry, had significantly increased resistances at 5-25 Hz and decreased reactances at 10-35 Hz. In never-smoking subjects, identical FOT signs were found.
pSS patients showed FOT signs of obstruction affecting both peripheral and central airways. pSS patients without spirometric signs of OAD and never-smoking pSS patients also showed clear FOT signs of obstruction. FOT therefore seems to be a sensitive method for detecting obstruction in pSS patients.