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The CellSearch™ Epithelial Cell Kit is intended for the enumeration of circulating tumor cells (CTC) of epithelial origin (CD45-, EpCAM+, and cytokeratins 8, 18+ and/or 19+) in whole blood. The presence of CTC in the peripheral blood, as detected by the CellSearch™ Epithelial Cell Kit, is associated with decreased progression free survival and decreased overall survival in patients treated for metastatic breast cancer.

The CellSearch™ Epithelial Cell Kit analyzed on the CellSpotter™ Analyzer is called the CellSearch Assay. The CellSearch Assay is a semi-automated in vitro diagnostic device. Epithelial cells are immunomagnetically labeled by targeting the Epithelial Cell Adhesion Molecule (EpCAM) antigen. Anti-EpCAM monoclonal antibodies conjugated to ferrofluid particles are colloidal and, when mixed with a sample containing the target epithelial cells, bind to the EpCAM antigen associated with the epithelial cells. After immunomagnetic selection of epithelial cells from 7.5 mL of blood, fluorescent reagents are added at this time to discriminate between the immunomagnetically selected cells. Anti-Cytokeratin - Phycoerythrin (CK-PE) stains the intracellular cytoskeleton cytokeratin proteins expressed in cells of epithelial origin, anti-CD45-Allophycocyan (CD45-APC) stains leukocytes and DAPI stains DNA present in the cell nucleus. A strong magnetic field is applied to the processed reagent/sample mixture that causes the labeled target cells to move to the cartridge surface. The cartridge is then placed on the CellSpotter™ Analyzer for data acquisition and analysis. The CellSpotter™ Analyzer acquires images of PE, APC and DAPI fluorescence staining of the entire viewing surface. After data acquisition is completed, the images are analyzed for any event where cytokeratin-PE and DAPI are within a specified space in the CellSpotter™ Cartridge, i.e. indicating the possible presence of a cell with a nucleus that expresses cytokeratin. Images from each fluorescent color as well as a composite image of the cytokeratin staining (green) and the nuclear staining (purple) are presented to the user in a gallery for final cell classification. A cell is classified as a tumor cell when it its EpCAM+ (i.e., it is captured), CK+, DAPI+ and CD45-. A check mark placed by the operator next to the composite images classifies the event as a Circulating Tumor Cell (CTC) and the software tallies all the checked boxes to obtain the CTC count.