A 24-Hour Extended Calibration Strategy for Quantitating Tacrolimus Concentrations by Liquid Chromatography-Tandem...

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Pharmacokinetics

Background:

• Tacrolimus monitoring requires strict control due to its narrow therapeutic index.
• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers accurate tacrolimus quantitation but often involves inefficient batch testing.
• Current methods necessitate frequent recalibration, impacting turnaround time and cost.

Purpose of the Study:

• To validate a 24-hour extended calibration strategy for LC-MS/MS tacrolimus assays.
• To reduce calibrator usage and associated costs.
• To improve laboratory workflow efficiency and reduce turnaround time for urgent patient samples.

Main Methods:

• Patient samples were extracted and assayed with co-extracted calibrators in real-time.
• The same samples were re-extracted 24 hours later without new calibrators.
• Data from the extended calibration were compared to results obtained with fresh calibrations.

Main Results:

• A strong correlation (R² > 0.95) was observed between results from the extended calibration and fresh calibrations.
• Linear regression analysis showed a slope of 1.0061.
• The average bias between the two methods was 3.4% across all patient samples.

Conclusions:

• Tacrolimus whole blood concentrations determined using a 24-hour extended calibration are comparable to those obtained with fresh calibrations.
• This extended calibration approach enables rapid turnaround times for urgent tacrolimus testing.
• The validated method supports a more efficient laboratory workflow and reduces testing costs.