Clinical efficacy of the Abbott Tacrolimus II assay for the IMx.

A B S T R A C T Monitoring tacrolimus is essential to maintain therapeutic concentrations. Perfor­ mance of the new Abbott Tacrolimus assay (FK II) was evaluated and com pared to the original tacrolimus assay (FK I). 189 trough whole blood samples from transplant cases w ere included in the study. Samples (n = 117) with FK I concentrations > 5 ng/mL w ere reanalyzed with the FK II assay. Patient samples (n = 43) that had FK I concentration < 5 ng/mL with apparent m ean and range of 3.1 ng/mL and 0.7 to 4.5 ng/mL, respectively, were also reanalyzed with FK II to yield a m ean of 5.9 ng/mL with a range o f 2.9 to 10.8 ng/mL. Checking for patient compliance, samples (n = 10) with a FK I concentration of 0 ng/mL were re-analyzed. W ith one exception of a mislabeled cyclosporine sample, all samples (n = 9) showed FK506 levels greater than 2 ng/m L with the FK II assay. The FK II assay was shown to be a clinically efficacious assay, with im proved sensitivity and acceptable precision versus the pre­ vious FK I assay.