Serum and pleural fluid levels of CA50 in malignant and tuberculous effusions.

The measurement of CA50 in serum and pleural fluid by immunoradiometric assay was presented in 45 (27 malignancy and 18 tuberculosis) patients with pleural effusion. The mean CA50 level in malignant effusion (89.26 +/- 122.32 U ml-1) was significantly higher than that in tuberculous effusion (5.18 +/- 8.65 U ml-1) (P < 0.001). CA50 levels of pleural fluid above an arbitrary level of 20 U ml-1 were found in 78% of malignant fluids and in 6% of tuberculous fluids. The serum CA50 value from 27 patients with malignant effusion (58.67 +/- 85.85 U ml-1) was also higher than that from 18 patients with tuberculous effusion (6.18 +/- 8.37 U ml-1) (P < 0.001). CA50 levels of serum above the same level were found in 58% of patients with malignant fluid and in 6% of patients with tuberculous fluid. The results suggested that the measurement of CA50 in pleural effusion may be helpful in the differential diagnosis between tuberculous and malignant effusions.