Comparison of HPLC-MS/MS and Enzyme-multiplied Immunoassay in Tacrolimus Determination and its Application in Therapeutic Drug Monitoring

The objective of this study is to compare the correlation of HPLC-MS/MS and enzyme-multiplied immunoassay technique (EMIT), for the determination of tacrolimus (FK506) concentration in human blood and to provide evidence for its rational usage in practice. Blood samples, collected from 346 liver and kidney organ transplant patients in Qilu Hospital of Shandong University, were determined by two methods. The calibration curves were linear within the range of 1.0-30.0 ng/mL for HPLC-MS/MS and 2.5-25 ng/mL for EMIT, respectively. The inter- and intra-day RSDs were less than 15%. The correlation of the two methods was good (r(2) = 0.989). Tacrolimus blood concentration, determined by EMIT, was 0.11 ng/mL more than HPLC-MS/MS. The 95% confidence interval was -0.24 similar to 0.46 ng/mL. There were no significant statistical differences between the two methods (P > 0.05). The HPLC-MS/MS and EMIT methods were suitable for determining tacrolimus blood concentrations. The correlation between the two methods was very good, but tacrolimus blood concentration determined by EMIT was higher than HPLC-MS/MS. Its clinical significance needs to be further evaluated.