Assessment of interlobar variation of bronchoalveolar lavage cellular differentials in interstitial lung diseases

Alveolitis is thought to precede permanent lung derangement in a variety of interstitial lung diseases (ILD). Bronchoalveolar lavage (BAL) cell differentials can be used to evaluate the intensity of alveolitis, whereas clinical, roentgenographic, and functional studies are insensitive monitors of lung inflammation. As ILD is generally diffuse, unilobar lavage is widely used and presumed to gauge overall lung inflammation. Consistency of lobe to lobe cell differential findings has not been systematically addressed. We analyzed 53 bilateral lobar lavages (right middle lobe and lingula) in 34 patients with sarcoidosis, idiopathic pulmonary fibrosis-collagen vascular disease (IPV-CV) and a group of mixed interstitial diseases. Cellular differentials from each lobe were independently assessed and compared. The sarcoid group, with predominantly T-lymphocytes in BAL, showed excellent interlobar correlation (r = 0.92, p < 0.001), with only 17% showing a discrepancy of >10% in percentage of T-lymphocytes. In contrast, the IPF-CV group, with predominantly neutrophils in BAL, showed good interlobar correlation (r = 0.79; p < 0.01), but 35% had a >10% discrepancy in percentage of neutrophils. Finally, the mixed group, with lymphocytes as the preodminant cell in BAL, showed poor interlobar correlation (r = 0.58; p > 0.10), with 42% showing a >10% discrepancy in percentage of lymphocytes. These results were not explicable on the basis of differences in volume of lavage fluid or total cells recovered, these parameters being remarkably consistent between lobes in the 3 patient groups and in a control group of 8 subjects with ILD. The chest roentgenogram was markedly insensitive to lavage interlobar variation. Of the 14 patients with >10% interlobar cell variation, only 3 demonstrated focal roentgenographic abnormality in the right middle lobe or lingula. These findings suggest that only in sarcoidosis are BAL interlobar cellular differentials reliably consistent. Future prognostic and therapeutic studies using BAL in ILD should take into account possible regional inhomogeneity of cellular events.