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

Abstract

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. 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. 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. 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.