Neutrophil-to-lymphocyte ratio in bronchoalveolar lavage from IPF patients: a novel prognostic biomarker?

BACKGROUND: This is the first time that a bronchoalveolar lavage (BAL) neutrophil-to-lymphocyte ratio (NL-ratio) has been demonstrated in sarcoidosis and chronic Hypersensitivity Pneumonitis (cHP) than in idiopathic pulmonary fibrosis (IPF) patients. SUBJECTS AND METHODS: Consecutive BAL samples from the 167 interstitial lung disease (ILD) patients were retrospectively enrolled in the study and clustered into three diagnostic categories: IPF, cHP and sarcoidosis. RESULTS: NL-ratio which proved higher in IPF (mean±SD, 2.1±3.8) than sarcoidosis (mean±SD 0.7±1.9; p<1E-04) and cHP patients (mean±SD 1.6±3.1; p=7.7E-03). ROC curve analysis to discriminate between Sarcoidosis and other ILDs showed an area under the curve (AUC) of 83.7%, (56% sensitivity and 96% specificity) while IPF and the other ILD were discriminated with AUC of 73% using a NL-ratio threshold value of 0.48 (73% sensitivity and 63% specificity). Interestingly, the NL-ratio was significantly correlated with other prognostic parameters: it was inversely correlated with forced vital capacity (FVC) (r=-0.3; p=2.5E-02) and forced expiration volume in 1 second (FEV1) (r=-0.3; p=2E-02) percentages and directly correlated with composite pulmonary index (CPI) score (r=0.3; p=3.2E-02). A decision-tree statistical algorithm was applied. CONCLUSIONS: This is the first time that a lower NL-ratio has been demonstrated in sarcoidosis and cHP than in IPF patients. The present preliminary report indicates a relationship between BAL NL- ratio and lung function parameters in patients with IPF: this ratio may help to optimize management of IPF patients and to improve follow-up and outcome.