Sialyl stage-specific embryonic antigen-1 - A useful marker for differentiating the etiology of pleural effusion

Objectives: To assess the usefulness of sialyl stage-specific embryonic ant igen-1 (SSEA-1) levels in differentiating the etiology of pleural effusion (PE), Design: A solid-phase immunoradiometric sandwich assay with an FH6 monoclon al antibody was used to measure sialyl SSEA-1 levels in PEs of 132 patients with various diseases. Paired serum sialyl SSEA-1 levels were measured sim ultaneously in 47 patients with various subtypes of lung cancer Results: The Pleural sialyl SSEA-1 levels were significantly higher in pati ents who had adenocarcinoma of the lung with positive cytology than in all the other patients, including those having malignancies other than adenocar cinoma of the lung, adenocarcinoma of the lung with cytology-negative PE, a nd benign diseases. There were no significant differences among sialyl SSEA -1 levels in the pleural fluid containing no adenocarcinoma cells. Using th e cutoff value of 265 U/mL, the sensitivity was 64% (25/39) and the specifi city was 95% (88/93) for the pleural sialyl SSEA-1 level to differentiate a denocarcinoma from other effusions, Conclusions: With high specificity and modest sensitivity, the pleural sial yl SSEA-1 level is a useful biochemical marker for differentiating the etio logy of PEs caused by adenocarcinoma from other diseases.