A complete blood count (CBC) is typically the first test requested by a physician to evaluate a patient’s general health status. For such screenings, automated hematology analyzes are frequently used. In addition to determine blood levels of platelets (PLT), red blood cells (RBC), and white blood cells (WBC), most analyzer can also differentiate WBCs into 3 (LYM, MID, GRAN) or 5 (LYM, MONO, NEU, EOS, BASO) subpopulations. Although a so called 3-part hematology analyzer provides sufficient information for most clinical settings, trends show an increased interest in 5-part instruments. While 5-part analyzers can offer more detailed information on the white blood cells, 3-part instruments can offer great cost benefits.