In another study prospectively investigating the OPN concentrations in pleural effusions of different aetiologies, researchers demonstrated that OPN levels were significantly elevated in exudative pleural effusions compared to those in blood or transudative effusions, and the higher pleural effusion/serum OPN ratio was observed in malignancies than that in tuberculous effusions [48], which could be useful for diagnostic purposes. The gene discussed is SPP1; the disease is Pleural effusion.