Patent ID: 6977156

Claim:
A method for preparing a sample of fresh human whole blood for cytometric analysis, comprising the steps of: a. contacting at least one leukocyte in said fresh blood sample while said fresh blood sample is still fresh with an aqueous reagent that includes: i. a lipoprotein agent for resisting lysing of white blood cells; and ii. an effective amount of an agent for lysing erythrocytes from said fresh blood sample; iii. a physiologically compatible salt; and iv. a preservative selected from the group consisting of diazolidinyl urea (DU), imidazolidinyl urea (IDU), an oxazolidine and mixtures thereof; b. binding said at least one leukocyte with a fluorescently labeled antibody; and c. analyzing said at least one leukocyte with an analytical instrument.