Tacrolimus Assay Comparison: Analytical and Operational Considerations for Immunoassay vs Mass Spectrometry Testing...

Area of Science:

• Clinical Chemistry
• Transplant Medicine
• Analytical Chemistry

Background:

• Tacrolimus monitoring is crucial for transplant recipients.
• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers accuracy but is labor-intensive.
• Immunoassays (IA) are faster but historically lacked specificity due to metabolite cross-reactivity.

Purpose of the Study:

• To compare the performance of the Roche Elecsys tacrolimus immunoassay with an in-house LC-MS/MS assay.
• To evaluate workflow improvements and turnaround times (TAT) after implementing the immunoassay.

Main Methods:

• A comparative analysis of 73 residual patient samples using LC-MS/MS and the Roche Elecsys immunoassay on a cobas® e801 analyzer.
• Statistical methods included Deming regression and Bland-Altman analysis.
• Evaluation of linearity, imprecision, workflow, and TAT.

Main Results:

• Excellent correlation was observed between the Roche Elecsys assay and LC-MS/MS (Deming regression: y = 1.004x + 0.4848).
• Bland-Altman analysis showed a bias of 0.52 ng/mL (8.1%).
• A 42%-51% improvement in TAT was achieved with the immunoassay.

Conclusions:

• The Roche Elecsys tacrolimus assay demonstrates excellent correlation, precision, and linearity compared to LC-MS/MS.
• Switching to the immunoassay significantly enhances workflow and reduces TAT in tacrolimus therapeutic drug monitoring.