Impact of Type of Tacrolimus Assay on Therapeutic Drug Monitoring: Need for Standardization
Internal Medicine/Nephrology, Washington University School of Medicine, St. Louis, MO.
Meeting: 2015 American Transplant Congress
Abstract number: C67
Keywords: Dosage, Graft function, Kidney transplantation
Session Information
Session Name: Poster Session C: Immunosuppression/Compliance
Session Type: Poster Session
Date: Monday, May 4, 2015
Session Time: 5:30pm-6:30pm
Presentation Time: 5:30pm-6:30pm
Location: Exhibit Hall E
Background: Multiple assays are available for measuring tacrolimus (FK) levels and these are not currently standardized. A designated laboratory transitioned their FK assay from Enzyme Multiplied Immunoassay Technique (EMIT) to Liquid Chromatography with Tandem Mass Spectrometry (LC-MSMS) during April and May 2013.
Methods: We analyzed the data on 393 patients transplanted between Jan 1993 and Dec 2012 from this designated laboratory who were on a stable dose of FK. The values of FK levels between January 2013 and August 2013 (3 months before and after the assay change) were also analyzed for these patients for comparison. Continuous variables are described as means with SD. The proportion of patients requiring dose change was described as a percentage. Paired T-tests were used to compare the mean FK level before and after the assay change.
Results: The table shows the results of the paired t-tests. There was a significant difference in the mean FK levels before and after the change in assay. After the adjustment in FK dose, there was no significant difference in the mean FK levels.
| Pairs | Mean | Standard Deviation | P-value |
| 1) Month 1 | 5.93 | 1.71 | 0.075 |
| 1) Month 3 | 5.65 | 1.86 | |
| 2) Month 1 | 5.95 | 2.14 | <0.001 |
| 2) Month 4 | 5.33 | 1.65 | |
| 3) Month 1 | 5.90 | 2.16 | <0.001 |
| 3) Month 5 | 3.76 | 1.57 | |
| 4) Month 5 | 3.77 | 1.76 | 0.297 |
| 4) Month 7 | 3.63 | 1.58 | |
| 5) Month 5 | 3.86 | 1.76 | 0.154 |
| 5) Month 8 | 3.61 | 1.73 | |
| Age | 53.95 | 14.92 | |
| Required dose change | 60 (15.3%) |
Conclusion: This study highlights the importance of the type of Tacrolimus assay on the FK levels and urgent need for standardization. The implementation of liquid chromatography with tandem mass spectrometry (LC-MSMS) technique as a standard could help standardize the reporting of FK levels. There is an urgent need to develop best practice guidelines for LC-MSMS methods for its use for routine FK measurement. This will help harmonize results across the diagnostic laboratories.
To cite this abstract in AMA style:
Singh M, Anwar S, Brennan D, Santos RDelos. Impact of Type of Tacrolimus Assay on Therapeutic Drug Monitoring: Need for Standardization [abstract]. Am J Transplant. 2015; 15 (suppl 3). https://atcmeetingabstracts.com/abstract/impact-of-type-of-tacrolimus-assay-on-therapeutic-drug-monitoring-need-for-standardization/. Accessed May 12, 2025.« Back to 2015 American Transplant Congress