ABSTRACT
BACKGROUND: The KCl hypotonic treatment is important for swelling the cells and adequate spreading of chromosomes on the slide. Cytogenetic laboratory usually use 0.075M KCl solution. Sometimes, it is difficult to obtain enough and good quality of metaphase cells, because of inadequate hypotonic treatment. The purpose of this study was to evaluate the mitotic index and band resolution according to the different KCl concentration. METHODS: The group I included blood specimens obtained from 14 newborns (median age 1 day, range 1-8 days) and 4 cord blood. The group II included 16 persons whose median age was 28 years (1-37 years). The blood was cultured in RPMI 1640 medium with fetal calf serum and phytohemagglutinin for 72 hours. Mitosis was arrested by adding colcemid (100 ng/mL). The hypotonic treatment was done by adding different KCl concentration such as 0.075M, 0.068M and 0.057M for 30 minutes at 37 degrees C. The mitotic index was calculated as the number of metaphase cells per total 1,000 cells. The band resolution was evaluated by 2 persons independently. RESULTS: For group I, the mitotic index was not different according to the KCl concentration; 0.075M, 18.8 (5.5~31.5); 0.068M, 22.3 (11~32.5); 0.057M, 20.5 (2.5~29), (P=0.137). The proportion of cells with 400 or more band resolution was significantly higher in specimens treated with 0.068M KCl than those treated with 0.075M KCl; 0.075M, 67.8% (56~92.5); 0.068M, 73.6% (46.1~84.6); 0.057M, 71.6% (63~89.2), (P=0.027). For group II, the results were similar to those of group I. The mitotic index was as follows; 0.075M, 22.3 (5~28); 0.068M, 26 (4~34.5); 0.057M, 21.5 (2.5~36.5), (P=0.568). The proportion of cells with 400 or more band resolution was as follows; 0.075M, 66.6% (42.8~83.3); 0.068M, 69.7% (54.3~87.5); 0.057M, 68.2% (50~78.6) (P=0.04). CONCLUSIONS: For 0.068M or 0.057M KCl treatment, band resolution was improved, while the mitotic index was similar to that of 0.075M KCl. We suggest use of 0.068M or 0.057M KCl hypotonic treatment in addition to 0.075M KCl for chromosome preparation of peripheral blood.