Clinical efficacy of the Abbott tacrolimus II assay for the IMx (R)

Monitoring tacrolimus is essential to maintain therapeutic concentrations. Performance of the new Abbott Tacrolimus assay (FK II) was evaluated and co mpared to the original tacrolimus assay (FK I). 189 trough whole blood samp les from transplant cases were included in the study. Samples (n = 117) nit h FK I concentrations >5 ng/mL were reanalyzed nith the FK II assay. Patien t samples (n = 43) that had FK I concentration <5 ng/mL nith apparent mean and range of 3.1 ng/mL and 0.7 to 4.5 ng/mL, respectively, were also reanal yzed nith FK II to yield a mean of 5.9 ng/mL with a range of 2.9 to 10.8 ng /mL. Checking for patient compliance, samples (n = 10) nith a FK I concentr ation of 0 ng/mL were re-analyzed. With one exception of a mislabeled cyclo sporine 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 effica cious assay, nith improved sensitivity and acceptable precision versus the previous FK I assay.