Quantification of cyclosporine and tacrolimus in whole blood. Comparison of liquid chromatography-electrospray mass spectrometry with the enzyme multiplied immunoassay technique.
OBJECTIVE
The aim of this work was to compare a validated liquid chromatography-mass spectrometry (LC-MS) method with the commercial enzyme multiplied immunoassay technique (EMIT) for cyclosporine and tacrolimus whole blood quantification.


METHODS
Samples of transplant patients receiving cyclosporine (n=38) or tacrolimus (n=41) were analyzed successively by LC-MS and EMIT. Several statistical approaches for method comparison were evaluated and Passing-Bablok and Bland-Altman analyses chosen.


RESULTS
Overestimations of the concentrations measured with EMIT compared to LC-MS were observed with means of 23% (range: 6% to 46%) for cyclosporine and 30% (range: -3% to 73%) for tacrolimus.


CONCLUSIONS
The EMIT demonstrated significant positive biases due to cross-reactions with metabolites. This indicates that, in some clinical situations, a selective method such as LC-MS is preferable for therapeutic drug monitoring in transplant patients.
Ansermot
Nicolas
N
Laboratory Medicine Service, University Hospitals of Geneva, Geneva, Switzerland.
Fathi
Marc
M
Veuthey
Jean-Luc
JL
Desmeules
Jules
J
Rudaz
Serge
S
Hochstrasser
Denis
D
D003429:Cross Reactions; D016572:Cyclosporine / Q000097:blood*; D017248:Enzyme Multiplied Immunoassay Technique; D006801:Humans; D007118:Immunoassay; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D016559:Tacrolimus / Q000097:blood*; D014181:Transplantation Immunology
D016572:Cyclosporine; D016559:Tacrolimus