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Characterization of circulating antibodies with affinity to an epitope used in antibody-conjugated magnetic immunoassays from a case of falsely elevated cyclosporine A.

 Sunyoung Ahn  ;  Jooyoung Cho  ;  Soon Il Kim  ;  Jisook Yim  ;  Sang-Guk Lee  ;  Jeong-Ho Kim 
 Clinica Chimica Acta, Vol.458 : 35-39, 2016 
Journal Title
 Clinica Chimica Acta 
Issue Date
Adult ; Antibodies, Monoclonal/blood* ; Antibodies, Monoclonal/immunology* ; Cyclosporine/blood* ; Epitopes/immunology* ; Humans ; Immunoassay* ; Magnetic Phenomena* ; Male
Antibody-conjugated magnetic immunoassay ; Assay interference ; Cyclosporine ; Therapeutic drug monitoring
BACKGROUND: We report a case demonstrating falsely elevated cyclosporine A (CsA) levels by using the antibody-conjugated magnetic immunoassay (ACMIA). To determine the cause of the false positive result, we examined the presence of an interferent in the patient's sample. METHODS: A 26-year-old male patient displayed a high CsA concentration eight weeks after discontinuation of CsA treatment when measured by ACMIA. The possibility of assay interference was examined using serial dilution tests, heterophilic blocking tubes, erythrocyte washing, polyethylene glycol (PEG) protein precipitation, and a Protein A sepharose bead immunoabsorption assay. RESULTS: The serial dilution test showed nonlinearity, suggesting the presence of an interferent. CsA concentrations in the patient's plasma pre- and post-heterophilic blocking tube treatment were similar. Erythrocyte washing and PEG protein precipitation tests indicated the existence of a protein interferent in the plasma. Moreover, the Protein A bead immunoabsorption assay identified the interferent as antibodies against a unique epitope on the monoclonal antibody-β-galactosidase (mAb-β-gal) enzyme conjugate used in CsA ACMIA. CONCLUSIONS: We identified a circulating antibody against the unique epitope of the CsA ACMIA mAb-β-gal conjugate that induces falsely high CsA concentrations. These findings suggest that clinically aberrant CsA levels require immediate re-measurement by reference methods such as mass spectrometry.
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1. College of Medicine (의과대학) > Dept. of Surgery (외과학교실) > 1. Journal Papers
1. College of Medicine (의과대학) > Dept. of Laboratory Medicine (진단검사의학교실) > 1. Journal Papers
Yonsei Authors
김순일(Kim, Soon Il) ORCID logo https://orcid.org/0000-0002-0783-7538
김정호(Kim, Jeong Ho) ORCID logo https://orcid.org/0000-0003-2479-0548
이상국(Lee, Sang-Guk) ORCID logo https://orcid.org/0000-0003-3862-3660
임지숙(Yim, Jisook)
조주영(Cho, Jooyoung)
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