Improved mouse blood smears using the DiffSpin slide spinner.

Push smears of mouse blood prepared for differential white blood cell (WBC) determination often have many lysed WBCs, numerous RBC "ghosts", and poor morphology of intact RBCs. The purpose of this study was to compare the quality of peripheral blood smears prepared by 3 different methods and to optimize a technique for mouse blood differential WBC determination. Peripheral blood smears were prepared from blood obtained from clinically normal adult mice and human adults. Differential WBC counts, numbers of lysed WBCs/100 intact WBCs, and RBC morphology were compared in blood smears made using the standard push method with undiluted blood, the push method with blood diluted 1:5 with bovine serum albumin, and in centrifugally-prepared smears made with the DiffSpin Slide Spinner (StatSpin, Norwood, Mass, USA). The number of damaged WBCs in mouse versus human samples using the push method was compared using an unpaired Student's t test. ANOVA was used to compare differences in WBC differential counts and numbers of damaged WBCs among the 3 methods for each species. In addition, unpaired Student's t tests were used to compare each method against the other methods, within species. The number of damaged WBCs/100 intact WBCs was approximately 3 times higher in mouse than in human push smears (P=0.002). There was no significant difference in WBC differential cell counts among the 3 methods in either species. However, compared with both push techniques, a significantly (P <.01) greater number of intact cells was observed with the DiffSpin technique for mouse blood samples (damaged WBC/100 intact cells = 4.4 +/- 2.6 for DiffSpin smears, 9.5 +/- 3.9 for push smears with added albumin, and 31.3 +/- 10.2 for standard push smears). DiffSpin mouse blood smears consistently had better RBC morphology when compared with standard push smears. In conclusion, the DiffSpin Slide Spinner produced optimal smears of mouse blood for WBC differential determination and analysis of RBC morphology.