Analytical validation of the PRO-Trac II ELISA for the determination of tacrolimus (FK506) in whole blood

Background: The analytical validation of multiple lots of the PRO-Trac(TM) II ELISA (DiaSorin) for the determination of tacrolimus in whole blood is d escribed. Methods: The analytical parameters assessed included analytical sensitivity , dilution linearity, functional sensitivity,values in samples containing n o tacrolimus, intra- and interassay precision, supplementation and recovery , metabolite cross-reactivity, interference studies, and method comparisons HPLC-tandem mass spectrometry (HPLC/MS/MS) and the IMx(R) Tacrolimus II mu ltiparticle enzyme immunoassay. Where appropriate, assessments were perform ed according to NCCLS guidelines. Results: The mean analytical detection limit was <0.25 mu g/L for all lots, whereas the functional sensitivity was 1.0 mu g/L. Excellent linear correl ation (r = 0.985) was observed for dilution linearity. The intraassay impre cision was <7%, and the total imprecision by ANOVA was <10%. Recovery was 1 09% +/- 11%. Metabolite cross-reactivity was consistent with previous repor ts for this antibody. No interference was observed for 35 tested drugs. Met hod comparison with HPLC/MS/MS showed no statistically significant differen ces. Samples exhibited stability through four freeze/thaw cycles and for 1 week at room temperature. Conclusion: These data demonstrate that the PRO-Trac II ELISA is a robust, accurate, and precise tool for the assessment and management of tacrolimus blood concentrations in transplant patients. (C) 1999 American Association for Clinical Chemistry.