On the basis of results of the mixed model , during the study , patients in the LD group had significantly lower trough blood levels of rapamycin ( mean range SD , 2.40 0.64 to 2.90 1.20 ng/ml ) compared with those in the STD group ( 3.93 2.27 to 5.77 1.06 ng/ml ) ( P < 0.01 ) .