Is the affinity column-mediated immunoassay method suitable as an alternative to the microparticle enzyme immunoassay method as a blood tacrolimus assay?
BACKGROUND
Tacrolimus is a potent immunosuppressive drug used in organ transplantation. Because of its substantial toxic effects, narrow therapeutic index, and interindividual pharmacokinetic variability, therapeutic drug monitoring of whole-blood tacrolimus concentrations has been recommended. We investigated the comparability of the results of 2 immunoassay systems, affinity column-mediated immunoassay (ACMIA) and microparticle enzyme immunoassay (MEIA), comparing differences in the tacrolimus concentrations measured by the 2 methods in relation to the hematologic and biochemical values of hepatic and renal functions.


METHODS
A total of 154 samples from kidney or liver transplant recipients were subjected to Dimension RxL HM with a tacrolimus Flex reagent cartilage for the ACMIA method and IMx tacrolimus II for the MEIA method.


RESULTS
Tacrolimus concentrations measured by the ACMIA method (n = 154) closely correlated with those measured by the MEIA method (r = 0.84). The Bland-Altman plot using concentration differences between the 2 methods and the average of the 2 methods showed no specific trends. The tacrolimus levels determined by both the MEIA method and the ACMIA method were not influenced by hematocrit levels, but the difference between the 2 methods (ACMIA - MEIA) tended to be larger in low hematocrit samples (P < .001).


CONCLUSIONS
The ACMIA method used for a tacrolimus assay is precise and has advantages, including the lack of a required pretreatment procedure. Furthermore, it is only slightly influenced by the hematologic or biochemical status of the samples.
Ju
M K
MK
Department of Surgery, Yonsei University College of Medicine, Seoul, Republic of Korea. ysms91@yuhs.ac
Chang
H K
HK
Kim
H J
HJ
Huh
K H
KH
Ahn
H J
HJ
Kim
M S
MS
Kim
S I
SI
Kim
Y S
YS
D001663:Bilirubin / Q000097:blood; D002846:Chromatography, Affinity / Q000379:methods; D003404:Creatinine / Q000097:blood; D006400:Hematocrit; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007124:Immunoenzyme Techniques; D007166:Immunosuppressive Agents / Q000097:blood* / Q000627:therapeutic use; D016030:Kidney Transplantation / Q000276:immunology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012709:Serum Albumin / Q000032:analysis; D016559:Tacrolimus / Q000097:blood* / Q000627:therapeutic use*
D007166:Immunosuppressive Agents; D012709:Serum Albumin; D003404:Creatinine; D001663:Bilirubin; D016559:Tacrolimus