DIFFERENCES IN BAL FLUID VARIABLES IN INTERSTITIAL LUNG-DISEASES EVALUATED BY DISCRIMINANT-ANALYSIS

The aim of this study was to investigate the possibility of distinguis hing between patients with similarities in clinical presentation, suff ering from three frequently occurring interstitial lung diseases, by m eans of discriminant analysis, using a number of selected variables de rived from bronchoalveolar lavage fluid (BALF) analysis. The study inv olved all 277 patients, who had an initial bronchoalveolar lavage (BAL ) in the period 1980-1990. These patients belonged to the following di agnostic groups: sarcoidosis (n=193), subacute extrinsic allergic alve olitis (EAA) (n=39) and idiopathic pulmonary fibrosis (IPF) (n=45). Th irty healthy volunteers were used as controls. Cellular and non-cellul ar constituents of BALF were evaluated. Variables, which could be used to discriminate among the three diagnostic groups were: yield of reco vered BALF, total cell count, and percentages of alveolar macrophages, lymphocytes, polymorphonuclear neutrophils, eosinophils and plasma ce lls in BALF. When the set of data used to predict the membership of pa tients to diagnostic groups (test set) was the same as that in which t he discriminant analysis was performed (learning set), 93% of the case s were correctly classified. This percentage decreased to 90%, however , when the test set was different from the learning set. It is possibl e to discriminate among patients with sarcoidosis, EAA or IPF with the se selected variables. It appears that bronchoalveolar lavage (BAL) is useful as an adjunct in concert with other diagnostic methods.