[Comparative study of the expression of CEA and a myelomonocytic antigen (CD15) in serous effusions using two monoclonal antibodies NEO 723 and Leu M1].

A comparative study of the reactivity of two monoclonal antibodies (MAb), NEO 723 (anti-CEA) and Leu M1 (CD15) was performed by immunocytochemistry on sixty five reactive effusions and sixty two neoplastic effusions, fifty eight due to metastases from carcinomas, two due to disseminations of sarcoma and two due to malignant mesotheliomas. The study of the expected reactivity of NEO 723 and the cross-reactivity of Leu M1 on exfoliated neoplastic cells in effusion fluids showed that the sensitivity of NEO 723 was superior to that of Leu M1 for the detection of carcinomatous metastases, as 78% reacted with NEO 723 versus 38% with Leu M1. Among the positive cases, the mean number of reactive cells was twice as high with NEO 723, while only three of the carcinomas no expressing CEA reacted with Leu M1. The study of the reactivity of benign and malignant mesothelial cells with these two antibodies also confirmed the absence of labelling of these cells. Thus, despite a good specificity for carcinoma, the combination of these two antibodies provides only a minor gain in diagnostic sensitivity (+5%) compared with the use of an anti-CEA antibody alone and a loss of sensitivity (-5%) compared with the combination of an anti-CEA and an anti-EMA antibodies. These results appear to justify the suppression of Leu M1 from the first panel of antibodies screening for carcinomatous cells in favour of a combination of anti-CEA and an anti-EMA antibodies. However, Leu M1 may be useful as a second-line test in order to define the primary tumour responsible for the effusion.