BAL biomarkers' panel for differential diagnosis of interstitial lung diseases

Bronchoalveolar lavage (BAL) is a useful procedure for differential diagnosis of interstitial lung diseases (ILDs) and for identification of granulomatous lung diseases. We investigated a panel of biomarkers from BAL fluid of ILD patients to evaluate their utility in differentiating ILDs. Bronchoscopy with BAL was performed in 100 consecutive patients with suspected ILD (41 sarcoidosis, 11 cHP and 24 other ILDs); the 24 patients negative for ILD diagnosis were included as control group. BAL phenotypes and cell profiles (CD4⁺/CD8⁺ ratio, NK and CD103⁺ cell counts, chitotriosidase and KL-6 levels in BAL) were determined by flow cytometry. A decision-tree statistical algorithm was applied. Sarcoidosis was discriminated by a higher BAL CD4⁺/CD8⁺ ratio (p = 5.8E-05), a lower BAL CD103⁺CD4⁺ count (p = 5.0E-02) and lower BAL NK percentages (p = 8.8E-03) than the other groups. BAL KL-6 concentrations were higher in sarcoidosis than in other ILDs (p = 1.5E-02) and were directly correlated with CD4⁺/CD8⁺ ratio. We used decision-tree statistical analysis to combine our biomarkers into two diagnostic algorithms for differential diagnosis of ILDs. A panel of BAL biomarkers for diagnosis of ILDs is proposed; CD4⁺/CD8⁺ ratio, KL-6 concentrations, and NK and CD103⁺CD4⁺ cell percentages in BAL could improve the identification and differential diagnosis of sarcoidosis.