Flow cytometry is a modality with ever increasing applications in modern hematological, microbilogical and immunological fields. This is due to rapidity of obtaining results, ease of use and insreasing power to detect abnormal populations of cells. Recent advances in the availabilty and reproducibility of monoclonal antibody reagents specific for a wide range of of cell types coupled with lower costs for increasingly automated flow cytometers and user data analysis capabilities have made flow cytometry the method of choice for immunophenotyping in the clinical laboratory (Dunphy 2004).