A sample processing method for immunoassay of whole blood tacrolimus

Area of Science:

• Clinical Chemistry
• Biochemistry
• Assay Development

Background:

• Current tacrolimus (FK506) immunoassays rely on organic solvent and metal ion extraction.
• These methods present operational challenges, automation difficulties, and potential measurement bias.

Purpose of the Study:

• To develop a new sample processing (SP) reagent for tacrolimus (FK506) quantification in whole blood.
• To establish a time-resolved fluorescence immunoassay (TRFIA) using the novel SP reagent.

Main Methods:

• A new SP reagent was developed for blood cell lysis and protein denaturation.
• A TRFIA was optimized for whole blood FK506 quantification using the SP reagent.
• No centrifugation was required after sample processing.

Main Results:

• The SP reagent created a homogeneous blood solution suitable for direct immunoassay application.
• The FK506-TRFIA demonstrated analytical sensitivity of 0.57 ng/mL with CVs <10%.
• Excellent correlation (R²=0.982) was observed with a commercial chemiluminescence immunoassay (CMIA), and high resistance to interferences was confirmed.

Conclusions:

• The novel SP method offers a simplified and more automatable approach for FK506 immunoassays.
• This method overcomes limitations of traditional extraction techniques, enhancing assay feasibility.