Method for determining a concentration of epithelial cells in a blood sample or aspirate sample

A method for determining a concentration of epithelial cells in a blood sample or aspirate sample which originates from a human or mammal and has been admixed with an anticoagulant, comprising the following steps:

• a) lysing the erythrocytes present in the blood sample or aspirate sample by addition of a buffer which brings about a lysis of the erythrocytes, segregating cells which are not lysed in the course of this, and suspending the segregated cells in a buffer, wherein the blood sample or the aspirate sample is stored at a temperature between 0 and 40° C. for at least 24 hours before the erythrocytes are lysed,
• b) adding antibodies, antibody fragments or antibody mimetics which each bear at least one label and which are each directed against the epithelial cell adhesion molecule (EpCAM) and/or at least one other antigen specific for epithelial cells to a cell suspension obtained in step a) or to a subquantity of said cell suspension, which subquantity has been obtained by segregation, mixing the antibodies, antibody fragments or antibody mimetics and the cell suspension or the subquantity, and incubating a mixture obtained as a result for at least a time which is required for the attainment of a decreasing binding rate of binding of the antibodies, antibody fragments or antibody mimetics to the cells, wherein the incubation is done for at least 12 hours,
• c) determining the number of cells labeled by binding of the antibodies, antibody fragments or antibody mimetics, in the mixture obtained in step b), and
• d) calculating the concentration of the labeled cells, the number of which has been determined in step c), in the blood sample or aspirate sample.