Comparison of CEDIA FK506 assay with HPLC/MS/MS in a large cohort of pediatric patients

Area of Science:

• Pharmacology
• Clinical Chemistry
• Transplantation Medicine

Background:

• FK506 (tacrolimus) is a crucial immunosuppressant for pediatric transplant recipients.
• Accurate monitoring of FK506 whole blood levels is essential due to its narrow therapeutic window in children.
• High-pressure liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) is the gold standard but is labor-intensive.
• Cloned enzyme donor immunoassay (CEDIA) offers a less time-consuming alternative.

Purpose of the Study:

• To compare the accuracy and reliability of CEDIA and HPLC/MS/MS for quantifying FK506 levels in pediatric transplant patients.
• To identify potential biases and discrepancies between the two assay methods across different transplant types.

Main Methods:

• Simultaneous analysis of 348 split samples using both CEDIA and HPLC/MS/MS.
• Stratification of an additional 70 samples by organ transplant type (cardiac, renal, small bowel, liver).
• Application of standard statistical techniques, including Bland-Altman analysis, for method comparison.

Main Results:

• CEDIA demonstrated significant inaccuracy, overestimating FK506 by >20% in 40% of samples and underestimating by >20% in 13.5%, totaling 53% inaccuracy (±20% cutoff).
• Only 28% of samples analyzed by CEDIA were within 10% of HPLC/MS/MS values.
• Bland-Altman analysis revealed a mean bias of 9.5% favoring CEDIA, with the greatest positive bias observed in liver transplant patients.
• Lowest agreement (R² values) between methods was noted in intestinal transplant recipients.

Conclusions:

• CEDIA exhibits substantial variability and inaccuracy in monitoring FK506 levels in pediatric transplant patients compared to HPLC/MS/MS.
• The observed bias and inaccuracy suggest caution when using CEDIA, particularly for liver and intestinal transplant recipients.
• HPLC/MS/MS may be the preferred method for FK506 monitoring in certain pediatric transplant subgroups, especially intestinal transplant patients, to ensure optimal therapeutic management.