Multicenter evaluation of a new inosine monophosphate dehydrogenase inhibition assay for quantification of total mycophenolic acid in plasma.
The performance characteristics of a new inosine monophosphate dehydrogenase inhibition assay for the quantification of total mycophenolic acid (MPA) in plasma (Roche Diagnostics) were assessed in a multicenter evaluation. Validation data were collected from four institutions. Within-run and total imprecision were acceptable (n = 21 for each of 7 materials, coefficients of variation ranging 0.7-9.6%). The lower limit of quantification was 0.31 mg/L. The assay was linear from 0.31 to 15.0 mg/L. Method comparison with validated high-performance liquid chromatography with ultraviolet light or liquid chromatography tandem mass spectrometry methods showed good agreement (coefficients of correlation 0.974-0.994, slopes 1.01-1.17, intercepts -0.17 to 0.06). There was no difference found between results from different transplant types (cardiac vs. renal) or comedications (cyclosporine vs. tacrolimus). The recovery of samples from a proficiency testing scheme was acceptable. The cross-reactivity of AcMPAG, an in vitro active metabolite of MPA, was examined by adding AcMPAG to a pool of patient samples and subsequent quantification. MPA overestimation by AcMPAG cross-reactivity was found to be low (<5%). Thus, this interference is expected to be clinically irrelevant. In conclusion, the Roche Total MPA assay is a promising alternative for MPA quantification where chromatographic methods are not available.
Brandhorst
Gunnar
G
Department of Clinical Chemistry, University Hospital Goettingen, Germany. gunnar.brandhorst@med.uni-goettingen.de
Marquet
Pierre
P
Shaw
Leslie M
LM
Liebisch
Gerhard
G
Schmitz
Gerd
G
Coffing
Mary Jane
MJ
Domke
Ingrid
I
Streit
Frank
F
Luthe
Hilmar
H
Oellerich
Michael
M
D000918:Antibody Specificity; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions; D016903:Drug Monitoring; D004791:Enzyme Inhibitors / Q000097:blood* / Q000494:pharmacology*; D006801:Humans; D007168:IMP Dehydrogenase / Q000037:antagonists & inhibitors* / Q000097:blood*; D007291:Inosine Monophosphate / Q000378:metabolism; D013058:Mass Spectrometry; D009173:Mycophenolic Acid / Q000097:blood*; D009243:NAD / Q000378:metabolism; D015203:Reproducibility of Results
D004791:Enzyme Inhibitors; D009243:NAD; D007291:Inosine Monophosphate; D007168:IMP Dehydrogenase; D009173:Mycophenolic Acid