[The Role of Bronchoalveolar Lavage in the Diagnosis of Idiopathic Pulmonary Fibrosis: An Investigation of the Relevance of the Protein Content].

Although bronchoalveolar lavage (BAL) is often used in the diagnosis of interstitial lung diseases (ILDs), its importance in investigating, in particular, idiopathic pulmonary fibrosis (IPF) is controversial. The cell distributions in the BAL are taken into account in the clinical routine, non-cellular characteristics of the BAL play no role.Using mathematical modeling of data, the present work investigated the extent to which BAL features enable drawing conclusions about the underlying ILK or help exclude IPF. Included in the calculation are cellular findings of the BAL, in addition the protein and albumin content of the BAL, the nicotine history (pack years), and spirometry (FEV1, IVC).Using linear discriminant analysis and creating classification trees, the relevance of the characteristics of 806 patients with ILK was examined (183 IPF, 191 cryptogenic organizing pneumonia, 147 lung involvement in autoimmune disease, 97 respiratory bronchiolitis interstitial lung disease, 118 extrinsic allergic alveolitis, 41 lymphocytic interstitial pneumonia (LIP), 23 non-specific interstitial pneumonia (NSIP), 88 controls).There was a close positive relationship between protein levels and lymphocytes in the group as a whole. No such correlations were seen in IPF and NSIP. Albumin was closely correlated with the protein content in all groups.The lymphocytes are best suited to distinguish between different ILDs. Yet, a reliable calculation of the ILD is not possible on the basis of the investigated factors, the classification error ranged from 23.5 % (IPF) to 100 % (LIP, NSIP).Constellations that likely (> 99 %) speak against an IPF are lymphocytosis > 34 % or protein content > 347 mg/l. The same applies to the constellation: lymphocytes > 25 % together with protein > 250 mg/l.In ILD, BAL findings can narrow the diagnosis, but they are seldom diagnostic. BAL can make an important contribution to excluding of IPF.