Compositions and methods for leukocyte differential counting

A method for classifying 5-leukocytes types in a leukocyte population with fluorescence detection, said method comprising:

• contacting a leukocyte population in a sample having one or more leukocyte types with a diagnostic composition, said diagnostic composition comprising:
• a first dye having a cationic charge, wherein said first dye is propidium iodide;
• a second dye having less cationic charge compared to said first dye, wherein said second dye is Basic Orange 21;
• and
• a third dye being reactive to a protein, wherein said third dye is fluorescein isothiocyanate having an affinity to a protein;
• exciting the stained leukocyte population with a light source;
• and
• measuring emitted light from each of the one or more leukocyte types to classify the leukocyte population, wherein the leukocytes in the population comprise a lymphocyte, a monocyte, a neutrophil, an eosinophil and a basophil.