S100A2: A potential biomarker to differentiate malignant from tuberculous pleural effusion

Background: S100 calcium binding protein A2 (S100A2)-which has been testified to have an abnormal expression in non-small cell lung cancer (NSCLC)-is considered as an effective biomarker in the diagnosis and prognosis of this malignancy. In this study, we detected the S100A2 levels in pleural effusion, aiming to evaluate its potential value in differentiating malignant pleural effusion (MPE) from tuberculous pleural effusion (TPE). Methods: We collected pleural effusion from 104 NSCLC patients with MPE and 96 tubercular pleurisy cases. Enzyme-linked immunosorbent assay (ELISA) was performed to measure the levels of S100A2 in these samples. Meanwhile, the serum S100A2 levels were also examined in same subjects. The data concerning the expression of those commonly-used markers, including CEA, CYFRA211 and NSE, were obtained from medical records. Results: Like other classified biomarkers, S100A2 had an over-expression in both pleural effusion and sera of the NSCLC patients compared with controls (P = 0.000), though having a lower P value. Receiver operating characteristic (ROC) analysis showed that the levels of S100A2 in pleural effusion (PE) could distinguish MPE from tuberculous pleurisy (Area Under the Receiver Operating Characteristic Curve (AUC) = 0.887), and its diagnostic value in hydrothorax was obviously higher than in serum (AUC = 0.709). Conclusion: Our results indicate that levels of S100A2 are significantly elevated in MPE, and that S100A2 may serve as a diagnostic biomarker for NSCLC patients with MPE. In further studies, we will validate our findings with a larger sample population.