Background The Dade Behring Syva(R) EMIT (enzyme multiplied immunoassay technique) method for the measurement of tacrolimus in whole blood was evaluated against the Abbott IMx(R) microparticle enzyme immunoassay (MEIA) method. EMIT measures tacrolimus colorimetrically, whereas MEIA measures the analyte using fluorimetry. Both methods incorporate a protein precipitation step prior to measurement.
Method Whole blood specimens were treated by two types of precipitation technique followed by analysis for tacrolimus by either MEIA or EMIT on the Bayer Advia 1650. Linearity and precision were assessed and correlation analysis performed to evaluate the EMIT assay on the Bayer Advia 1650.
Results The EMIT tacrolimus assay was linear over the concentration range 0.0-22.0 mug/L; the limit of detection was 1.2 mug/L. Correlation between the Syva EMIT and IMx tacrolimus assays was excellent (r=0.959) and no significant bias existed between the two methods (mean difference, delta = 0.221 mug/L). Calibration data for the EMIT assay was stable for a period of 24-48 h on the Advia between runs.
Conclusion The Syva EMIT assay for the measurement of tacrolimus in whole blood is suited for daily routine use on the Bayer Advia 1650.