Clearance of intravenous busulfan according to GST gene polyphorphisms. Each bar denotes mean and 95% confidence interval for each group. A+M+T+ is for GSTA1 *A/*A and present genotype of both GSTM1 and GSTT1; A+(MorT)+ for GSTA1 *A/*A and present genotype of GSTM1 or GSTT1; A+M-T- for GSTA1 *A/*A and null genotype of both GSTM1 and GSTT1; A-M+T+ for GSTA1 *A/*B and present genotype of both GSTM1 and GSTT1; A-(MorT)+ for GSTA1 *A/*B and present genotype of GSTM1 or GSTT1; and A-M-T- for GSTA1 *A/*B and null genotype of both GSTM1 and GSTT1.