Carcinoembryonic antigen titers on effusion fluid. A diagnostic tool?

Carcinoembryonic antigen (CEA) has been demonstrated in tumors and body fluids, suggesting that effusion fluid (EF) CEA titer might separate benign and malignant EF. Plasma and EF CEA titers were determined on 141 patients with either benign (86) or malignant (55) EF. Although plasma CEA titers separated patients with either a benign or malignant EF 56% of the time, this separation was better accomplished (90% of the time) using EF CEA (P less than .0001). A malignant EF was associated with an EF CEA titer greater than or equal to ng/ ml or when, in the range 5.0 to 9.9 ng/ml, the EF CEA titer was greater than twice the plasma CEA. Paired plasma and EF CEA titers may aid in determining the benign or malignant origin of an EF.