Comparison of liquid chromatography-tandem mass spectrometry method with a antibody-bound magnetic immünoassay method for the determination of whole-blood cyclosporine-A level

Cyclosporine A (CsA) is a cyclic endecapeptide and a potent immunosuppressive drug. It is used as an immunosuppressant to prevent rejection of transplant organs and bone marrow. Cyclosporine A is also used for the treatment of autoimmune diseases and graft-versus-host disease. Cyclosporine A exhibits a narrow therapeutic range between efficacy and toxicity. Cyclosporine A may cause numerous side effects including renal, hepatic and immunological complications and some of them are serious. Renal dysfunction and increased risk of developing malignant diseases such as lymphoma are some of the serious side effects. In addition, the inter-individual and intra-individual pharmacodynamics and pharmacokinetic variability of CsA is large. Therefore constant monitoring of the CsA concentration is mandatory. Several analytical methods are available for the determination of CsA in biological specimen for therapeutic drug monitoring purpose, such as immunoassays, liquid chromatography coupled with ultraviolet detection (HPLC-UV) and liquid chromatography coupled with mass spectrometry (LC/MS/MS). The aim of this study is to compare an immunoassay method, antibody conjugate magnetic immunoassay (ACMIA), with a more sensitive and selective method, liquid chromatography-tandem mass spectrometry (LC/MS/MS) for CsA determination. 50 volunteers using CsA drug due to various diseases included in this study. Two whole blood samples were drawn from each subject included in this study and analyzed with ACMIA and LC/MS/MS methods. In this comparative study, a correlation (r=0.857) was found between two methods. Regression analysis [LC/MS/MS method (x) and ACMIA (y)] yielded a slope of 1.437, an intercept of 25.66, and R2 0.735. There was a systematic deviation between LC/MS/MS and ACMIA (42% lower than ACMIA). It is possible to detect several immunosuppressants simultaneously, thus significantly lowering the cost of analysis. LC/MS/MS method is more sensitive, more selective and have a larger linear range for immunosuppressant drugs than the previously used immunoassay method. In conclusion, this method may be preferred to immunoassays for the routine clinical measurement of immunosuppressive drug concentrations in whole blood. Key Words: Cyclosporine A, liquid chromatography-tandem mass spectrometry, antibody conjugate magnetic immunoassay, therapeutic drug monitoring