Differential diagnosis of pleural effusions: clinical usefulness of cell marker quantitation.

Carcinoembryonic antigen (CEA), orosomucoid beta 2 microglobulin, and alpha fetoprotein were quantified in the pleural fluid and serum of 58 hospitalized consecutive patients in order to differentiate malignant from non-malignant effusions. Cytologic examination of the effusions was also performed. The orosomucoid assay was the most helpful in identifying malignant effusions; higher values (greater than 100 mg/100 ml) were found in 74 percent (26/35) of malignant effusions. Quantitation of carcinoembryonic antigen had a high specificity (95 percent) but a low sensitivity (36 percent) for the detection of malignant pleural effusions. The parallel quantitation of CEA and orosomucoid had a higher sensitivity (86 percent) which increased when associated with cytologic examination. The sensitivity of cytology was only 46 percent. The concentrations of orosomucoid in pleural effusions correlated well with serum concentrations. Alpha fetoprotein and beta 2 microglobulin quantitations were of no clinical value for diagnosing malignant effusions. It is suggested the cytologic examination combined with orosomucoid and CEA quantitation in pleural fluid have a considerable clinical value for the diagnosis of pleural effusions.