[The role of B cell activating factor in the differential diagnosis of usual interstitial pneumonia]

Objective: To explore the differential diagnostic role of B cell-activating factor(BAFF) in idiopathic pulmonary fibrosis (IPF) and usual interstitial pneumonia (UIP) associated with autoimmune diseases (AIDs). Methods: Plasma levels of BAFF were measured by ELISA method in 23 patients with AIDs-UIP, 34 patients with IPF, and 21 healthy subjects as control. The correlation between plasma BAFF levels and other clinical results from patients was analyzed. Receiver operating characteristics (ROC) analysis for distinguishing AIDs-UIP from IPF patients was examined and the maximal area under curve (AUC) was found. Results: Plasma levels of BAFF were significantly elevated in AIDs-UIP patients and IPF patients compared to healthy subjects(P<0.001 and P=0.002, respectively). AIDs-UIP patients had higher level of BAFF than IPF patients(P=0.030). Plasma BAFF levels in AIDs-UIP patients were inversely correlated with pulmonary function results, including FVC%(r=-0.435, P=0.040)and TLC%(r=-0.449, P=0.041), as well as DLCO%(r=-0.491, P=0.024). When the cut off value of BAFF was set as 1.5 ng/ml to distinguish AIDs-UIP patients from IPF patients, the sensitivity and the specificity was 64.5% and 90.0%, respectively, and the area under ROC curve reached the maximum of 0.784(P=0.000, 95% CI: 66.3%-90.5%). Conclusions: Plasma BAFF levels were significantly higher and inversely correlated with pulmonary function, reflecting the severity of AIDs-UIP patients. Plasma BAFF levels may be a useful marker for distinguishing AIDs-UIP from IPF.