Abstract: A universal blood diluent for use in hematology analysis is the subject of this invention. The diluent consists of an aqueous solution of 0.4-1.5% by weight of either Na.sub.2 SO.sub.4 or NaNO.sub.3 or a combination of the two. Also included is 0.1-0.4% by weight of a salt of the formula XH.sub.2 PO.sub.4 where X is either Na or K and 0.1-2.4% by weight of a salt of the formula X.sub.2 HPO where X is Na or K. The phosphate salts may be hydrous or anhydrous. A mixture of Na and K phosphate salts may also been employed. The salts should be present in a ratio of from 1:1 to 1:6 (by weight), XH.sub.2 PO.sub.4 :X.sub.2 HPO.sub.4. 0.1 to 1% by weight of one or both of NaCl and KCl is also included. The Na.sub.2 SO.sub.4 and NaNO.sub.3 should be present in a ratio of at least 1:1 (by weight) relative to the chloride salt. The pH of the diluent should be within the range of 6.0-8.0 and it should have an osmotic strength of 200-400 milliosmoles.

Abstract: Improved reagents and methods for obtaining distinct volumetric differentiation of platelets, erythocytes and certain leukocyute subpopulations are disclosed. 1,3-dimethylurea is disclosed as a cell stabilizing agent for use in the blood diluent reagent. A hematology analyzer detergent is described wherein the addition of a wetting agent to the diluent of the instant invention provides the necessary attributes of an automatic analyzer detergent. The lysing reagent exploits the selective and intrinsically gentle lytic qualities of the dodecyl quaternary ammonium salt. The improved method modifies the leukocytes so that the frequent lymphocyte and neutrophil subpopulations are well separated on a volume scale, permitting quantitative evaluation of infrequent and rare leukocyte subpopulations as well as improved enumeration of the lymphocytes and neutrophils.