Real-time reverse transcription-polymerase chain reaction assay for GA733-2 mRNA in the detection of metastatic carcinoma cells in serous effusions.

Cytomorphologic and immunocytologic examination alone provide only limited sensitivity for the detection of metastatic carcinoma cells in many cases of serous effusions. The specificity of conventional reverse transcription-polymerase chain reaction (RT-PCR) methods for detection of epithelial gene transcripts is low owing to the ectopic expression of many such genes in nonepithelial cells. For the detection of metastatic carcinoma cells, we describe a quantitative real-time RT-PCR assay for GA733-2 messenger RNA encoding an epithelial glycoprotein (EGP-2) that binds to the monoclonal antibody BerEP4. With serial dilutions of BerEP4-positive SK-BR-3 breast carcinoma cells, the RT-PCR assay was able to detect 10 carcinoma cells in a background of 10(6) lymphoid cells compared with 10(2) to 10(3) carcinoma cells detectable by immunocytologic examination. We analyzed 51 serous effusions, including 25 malignant metastatic effusions, by the real-time RT-PCR assay. Receiver operating characteristic curve analyses demonstrated a sensitivity of 96% corresponding to a specificity of 98% for a correct diagnosis of metastatic effusions. These results provide evidence that the GA733-2 real-time RT-PCR assay is a specific and sensitive tool for the detection of metastasis of BerEP4-positive primary tumors in serous effusion specimens.