Air trapping in primary Sjogren syndrome: Correlation of expiratory CT with pulmonary function tests

Purpose: The purpose of our study was to correlate the extent of air trappi ng on expiratory CT scans with results of pulmonary function tests (PFTs) i n a large group of patients with primary Sjogren syndrome and to determine whether these techniques may be complementary in assessing small airways ob struction. Method: Thirty-four nonsmoking patients with proven primary Sjogren syndrom e and 10 healthy nonsmokers underwent paired inspiratory-expiratory thin se ction CT and PFTs. Expiratory scans were scored for the presence and extent of areas of air trapping. Extent of air trapping was assessed visually and given a score. The functional significance of the extent of air trapping w as evaluated in both groups and then correlated with the results of PFTs. Results: Bronchiolar abnormalities were seen in 11 (32%) of 34 patients wit h primary Sjogren syndrome. On the expiratory CT scans, a mosaic pattern of lung attenuation was identified in 17 patients. Air trapping was found in 44 of 204 lobar observations on the expiratory scans. The median point scal e score at end-expiration was 3.6 (20%, Grade 1), ranging from 1 (5.5%, Gra de 1) to 9 (50%, Grade 2). The mean total score of air trapping was more pr evalent in lower (46/68) lobes (22.4%) than in upper (22/136) lobes (5.3%) (p < 0.001). PFTs were normal in the primary Sjogren syndrome patients as w ell as the healthy subjects. Air trapping was found more frequently in pati ents with primary Sjogren syndrome than in the healthy group. Only during e xhalation was there evidence of minimal lobular-sized areas or air trapping (Grade 1) in three of the healthy subjects. We did not find any correlatio n between air trapping and PFTs including the forced expiratory flow rate b etween 25 and 75% of the forced vital capacity (FEF25-75). Conclusion: Expiratory high resolution CT revealed the extent of bronchiola r disease in patients with primary Sjogren syndrome. We also found that the extent of air trappings did not correlate with PFTs, which suggests the ex istence of a subclinical bronchiolar inflammatory process that may precede detectable abnormalities in lung function tests.