The study of rare cell populations is important to advance medical diagnostics and therapeutics. For many clinical studies, rare cell counts promise to provide valuable alternate end points; examples are circulating tumour cells in peripheral blood, tumour stem cells, endothelial cells in blood, hematopoietic progenitor cells and their subpopulations, antigen specific T-cells and foetal cells in maternal circulation.
Flow cytometry is an established technology used in many research and clinical laboratories. The largest users are immunologists and haematologists who use it for cell sorting and analysis. Increasing requirements for processing larger numbers of patient samples led to the development of automated tube loading carousels and, later, multiwell plate-based sampling systems.