title: Effect of the hematocrit and its correction on the relationship between blood tacrolimus concentrations obtained using the microparticle enzyme immunoassay (MEIA) and enzyme multiplied immunoassay technique (EMIT).
abstract: The Abbott microparticle enzyme immunoassay (MEIA) and the Dade Behring enzyme multiplied immunoassay technique (EMIT) are the most frequently used methods in the therapeutic drug monitoring of tacrolimus; however, a hematocrit-dependent interference for the MEIA has been described. In 244 whole blood samples from patients with liver (n=152) and kidney (n=92) transplants, the MEIA/EMIT ratio presented a highly significant negative correlation with the hematocrit (r = -0.482, p < 0.001). On distributing the samples into three groups with a hematocrit of less than 30%, 30-40%, and higher than 40%, different regression equations were found between the results of MEIA and EMIT and demonstrate the different effect of the hematocrit on both immunoassays. Correcting the MEIA results by calculation for a hematocrit of less than 30% and higher than 40% (Hermida et al. Clin Lab 2005; 51: 43-45) led to a regression with EMIT that was similar to that found between MEIA and EMIT for the group of samples with a hematocrit of 30-40%. Furthermore, the corrected MEIA/EMIT ratio had a poor correlation with the hematocrit (r = 0.149, p < 0.05). In 95 samples with a hematocrit of less than 25% (n=73) and higher than 40% (n=22) we also determined the tacrolimus levels using the modified MEIA method to correct hematocrit interference, as proposed by Tomita et al. (Ther Drug Monit 2005; 27: 94-97). In the samples with a hematocrit of less than 25%, correcting the MEIA results by calculation produced results that were similar and had a high correlation coefficient (r = 0.954, p < 0.001) to those of the modified MEIA method, whose application as a routine practice is more expensive and laborious. Calculation of the corrected MEIA values in anemic patients may be useful for the therapeutic monitoring of tacrolimus.
authors.affiliation: Unidad de Monitorización de Fármacos, Laboratorio Central, Hospital Clínico Universitario, Santiago de Compostela, Spain.
authors.forename: Lorena
authors.initials: L
authors.lastname: Bouzas
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Ortega
authors.forename: Pedro
authors.initials: P
authors.lastname: Casado
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Arranz
authors.forename: Antonio
authors.initials: A
authors.lastname: Carcas
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Tutor
mesh_terms: D000740:Anemia / Q000097:blood; D016903:Drug Monitoring / Q000379:methods*; D006400:Hematocrit; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D007166:Immunosuppressive Agents / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016559:Tacrolimus / Q000097:blood*
chemical_list: D007166:Immunosuppressive Agents; D016559:Tacrolimus