ABSTRACT
Tacrolimus is one of the effective immunosuppressive drugs used after an organ transplant procedure. However, due to its narrow therapeutic range, its usefulness in preventing transplant rejection and minimizing nephrotoxicity is dependent on the monitoring of whole blood trough levels of tacrolimus. A 49-year-old kidney transplant recipient presenting with cough and general weakness was admitted to the hospital. Due to the patient's deeply compromised clinical condition, an immunosuppressive therapy was discontinued. Tacrolimus concentrations in the patient's whole blood samples were measured, using an automated chemiluminescent microparticle immunoassay (CMIA) instrument. Interference was suspected because tacrolimus concentrations after the discontinuation of tacrolimus dose were 20.9 and 18.2 ng/mL at day 2 and 3, respectively. Tacrolimus concentrations were 11.1 and 12.6 ng/mL, respectively, when re-tested using an antibody-conjugated magnetic immunoassay (ACMIA). We evaluated the relationship between the CMIA and ACMIA results, and calculated the expected values from the regression equation. Residuals were –8.4 and –4 ng/mL, respectively. There have been several cases with false detection of elevated tacrolimus concentrations using ACMIA; however, such falsely detected elevations using CMIA have rarely been reported. When unexpectedly high concentrations of tacrolimus are detected by CMIA in transplant patients, an immediate re-test using another technique might be necessary to rule out falsely elevated results.
Subject(s)
Humans , Middle Aged , Cough , Graft Rejection , Immunoassay , Kidney Transplantation , Kidney , Luminescence , Tacrolimus , Transplant Recipients , TransplantsABSTRACT
Tacrolimus is an immunosuppressive agent used to prevent post-transplantation rejection. Tacrolimus has a narrow therapeutic window and therefore, its whole blood concentration is measured for therapeutic drug monitoring. In this report, we present two cases of falsely elevated tacrolimus concentrations identified in recipients of solid organ transplants due to analytical interferences in the antibody-conjugated magnetic immunoassay (ACMIA) method used. Tacrolimus concentrations measured using ACMIA were 4- to 8-fold higher than the values obtained using liquid-chromatography-tandem mass spectrometry (LC-MS/MS) or chemiluminescent micro-particle immunoassay. The cause of this interference remains unknown, but the identification of a possible false elevation of tacrolimus is of paramount importance in clinical practice. Pre-treatment of samples by ethanol extraction or using alternative methods of tacrolimus measurement such as LC-MS/MS are necessary to obtain reliable results in the event of an analytical interference.
Subject(s)
Drug Monitoring , Ethanol , Immunoassay , Mass Spectrometry , Tacrolimus , TransplantsABSTRACT
A highly sensitive magnetic enzymE-linked chemiluminescent immunoassay method was developed for the detection of human chorionic gonadotropin(HCG). The monoclonal antibody was covalently coupled on the surface of carboxylated magnetic beads to generate magnetic-biotargeting; Alkaline phosphatase(ALP) was utilized as a labeled reagent of another monoclonal antibody, whereas 3-(2-spimadamantane) 4-methoxy-4-(3-phosphoryloxy)phenyl-1,2-dioxetane(AMPPD) was utilized as the chemiluminescent substrate. Based on this concept, a highly sensitive chemiluminescent immunoassay method was established to test HCG. Then, several modifications were made to optimize the method, and the detection sensitivity and procedure were improved accordingly. The detection of the assay could be fulfilled within 60 min and the test result of HCG concentration was linear over the range of 0.15 150 IU/L with good relativity(r=0.960). The relative standard deviation(RSD) were below 5% and the sensitivity of this method was 0.15 IU/L. The proposed method with wide linear range, simple operation and fast detection showed good prospect in practical application on-site.