Abstract: Objective：To assess the characteristics of establishing the different sample banks of plasma, leukocytes and DNA by sedimentation method of isolating from ethylene diamine tetraacetic acid（EDTA）-blood and to clarify the sedimentation method of leukocyte isolation and plasma volume by comparative data and recommended procedures for applicability. Methods:In the study, 29 EDTA-bloods were obtained, the total amounts of leukocytes and the percentage of neutrophile granulocytes, and lymphocytes in the EDTA-blood detected as a control group and then assigned equally into 4 EP tubes with 1 mL EDTA-blood per tube as 4 test groups, then the 4 tubes were placed with the EDTA-blood at room temperature and the plasma layers were isolated at 0.5, 1, 2 and 3 h, receptively. The total amount of leukocytes and the percentage of neutrophile granulocytes, and lymphocytes were detected by automated hematology analyzer at the clinical laboratory. The volume of the plasma was also measured at the same time. Results:The plasma volume at 0.5 h ［(241.72±101.52)μL］ was substantially lower than those at 1 h［(317.24±97.50)μL］, at 2 h［(371.03±91.66)μL］, and at 3 h ［(408.97±97.43)μL］ , P<0.05. The plasma volume at 1 h was substantially lower than those at 2 h and 3 h (P<0.05). The total amount of leukocytes in the plasma layer at 0.5 h (2.50 ×10⁶±1.48×10⁶) group was substantially higher than the amount of 2 or 3 h groups respectively (1.47×10⁶±7.19×10⁵ ,1.21 ×10⁶±7.41×10⁵), P<0.05. Significant difference was not found between 0.5 h group and 1 h group (2.29×10⁶±1.17×10⁶) , P>0.05. The total amount of leukocytes in the plasma layer in1h group was substantially higher than that in 2 h and 3 h groups (P<0.05). There was no significant difference between 3 h group and 2 h group (P>0.05). The total amount of leukocytes in the plasma layer of the 4 test groups was substantially lower than that in the control group (P<0.05). The percentage of neutrophile granulocytes (54.14%±11.65%) in the plasma layer in 0.5 h group was substantially higher than those in 1 h, 2 h and 3 h groups (46.66%±12.70%，39.17%±12.33%，43.25%±14.54%), P<0.05, respectively, which was the substantially lower than that in the control group (60.53%±8.46%), P<0.05. The average value of the percentage of neutrophile granulocytes in the plasma layer in 1 h group was substantially higher than that in 2 h group (P<0.05). There was no significant different between 3 h group and both 1 h, 2 h groups (P>0.05). The mean percentage of lymphocytes in the plasma layer in 0.5 h group (35.09%±10.84%) was substantially lower than those in the plasma layer in 1 h, 2 h and 3 h groups, respectively ( 41.48%± 12.20%, 47.96%±12.27%, 45.50%±13.71%), which was significant higher than that in the control group（30.98%±7.33%), P<0.05. The average value of the percentage of lymphocytes in the plasma layer in 1 h group was substantially higher than those in the control group and 0.5 h group, but was substantially lower than those in 2 h and 3 h groups (P<0.05). The average value of percentage of lymphocytes in the plasma layer in 2 h group was substantially higher than those in the control group, 0.5 h and 1 h groups (P<0.05). There was no significant difference between 2 h and 3 h groups (P>0.05). Conclusion:The best period of time in obtaining leukocytes is 0.5-1 h sedimentation of EDTA-blood. Both the plasma layer and leukocytes can be separated and obtained at the same time from the same sample by the sedimentation method of EDTA-blood. The sedimentation of EDTA-blood has the least interference of both chemical and physical factors, as well as a ready operation, which can establish the plasma, leukocytes and DNA sample banks for various aspects of research.

Key words: Blood sedimentation, Biological specimen banks, Plasma, Leukocyte count, DNA