Prevalence and clinical correlates of small airway obstruction in patients with systemic sclerosis

This study aims to assess the prevalence and clinical correlates of small airway obstruction (SAO) in patients with systemic sclerosis (SSc).

Sixty-nine consecutive patients with SSc (63 women and 6 men) were included. Lung function tests, including assessment of lung diffusing capacity, were performed in all patients. Patients were considered to have SAO when the maximal expiratory flow at 25% of the forced vital capacity (MEF₂₅) was lower than 60% as predicted. High-resolution computed tomography (HRCT) of the lung was performed in all patients with MEF₂₅ < 60%. We assessed the relationship of SAO in our patients with large airway obstruction, decreased lung diffusing capacity, HRCT findings, disease duration, disease subtype, scleroderma-specific antibodies, and smoking.

SAO was noticed in 46/69 (66.6%) of patients with SSc. Restrictive lung disease was found in 4/69 (5.8%), obstruction of large airways in 18/69 (26.1%), and decreased lung diffusing capacity in 47/69 (68.1%) of patients. No difference in gender, age, disease duration, disease subtype, and scleroderma-specific antibodies was found between patients with and without SAO. Eighteen out of forty-six (39.1%) patients with SAO had decreased forced expiratory volume in 1 sec (FEV₁) and the Tiffeneau-Pinelli index, indicating presence of coexistent large airway obstruction. Twenty out of forty-six (43.5%) patients with SAO had associated decreased lung diffusing capacity, while 8/46 (17.4%) of patients had isolated SAO. HRCT patterns of interstitial lung disease (ILD) were found more frequently in patients with SAO and decreased lung diffusing capacity, compared with patients with SAO and normal diffusing capacity (75% vs 11.5%, p = 0.008). We have noticed that tobacco smokers among SSc patients with SAO have more common associated obstructive lung disease on spirometry (58.8% vs 15.4%, p = 0.004). On the other hand, isolated SAO and SAO associated with impaired diffusing capacity were equally frequent among smokers and non-smokers.

Patients with SSc have commonly SAO. It can be considered clinical feature of undiagnosed asthma or chronic obstructive pulmonary disease (COPD), if isolated or associated with large airway obstruction, especially in tobacco smokers. On the other hand, SAO associated with decreased lung diffusing capacity was found to be not related to smoking, and may indicate a possible prominent bronchiolar involvement within SSc-related interstitial lung disease