Evaluation of an improved dot-immunobinding assay for carcinoembryonic antigen determination in nipple discharge in early breast cancer: results of a multicenter study.

We have previously reported carcinoembryonic antigen (CEA) measurement in nipple discharge to be a useful adjunct in the diagnosis of non-palpable breast cancer. We have now developed a "microdot-immunobinding assay" using a specially constructed device to screen efficiently large numbers of patients with nipple discharge for non-palpable breast cancer. The method is as follows: a sample of nipple discharge is placed on a solid phase monoclonal anti-CEA antibody and, if CEA is present in the discharge, it will be detected by a second monoclonal anti-CEA antibody conjugated with alkaline phosphatase. The use of bromochloroindolyl phosphate as a chromogen results in a stable color reaction that can be semiquantitatively analyzed with the naked eye. CEA levels determined by this microdot assay correlated well with those determined using the earlier Elmotec assay. To determine the accuracy of the method, a collaborative study involving 11 institutes in Japan was organized. The CEA levels in nipple discharges from 77 patients undergoing surgery, 44 of whom were diagnosed as having breast cancer, were assayed. The results were that 17 of the 23 patients with palpable breast cancer, and 16 of the 21 patients with non-palpable breast cancer exhibited CEA values > 400 ng/ml, a cut-off value determined in a previous study. The overall accuracy (78%) of this test for diagnosing non-palpable breast cancer was higher than that obtained from ductography or cytology. The system may thus be of use in the screening of early breast cancer.