Evaluation of a no-pretreatment cyclosporin A assay on the Dade Behring dimension RxL clinical chemistry analyzer.
BACKGROUND
Monitoring whole-blood concentrations of cyclosporin A (CsA) is common practice in the management of solid organ and bone marrow transplant recipients. In a multicenter study we evaluated a new, direct (no pretreatment) CsA assay on the Dade Behring Dimension RxL system and compared results with those from the Abbott TDx CsA immunoassay and a HPLC method.


METHODS
Whole-blood samples from heart (n = 111; 35 patients), liver (n = 201; 44 patients), kidney (n = 279; 65 patients), and miscellaneous organ (n = 77; 12 lung, 12 bone marrow, 5 kidney/pancreas, and 1 pancreas patient) recipients were obtained from patient populations of the participating institutions. Routine clinical monitoring of CsA was performed using either the TDx method or HPLC.


RESULTS
The minimum detectable concentration of CsA averaged 9.4 microg/L, and the lower limit of quantification was 30 microg/L. The method was linear from 30 to 500 microg/L. Cross-reactivity with seven different CsA metabolites ranged from 0.0% to 5.7% for the Dimension RxL assay compared with 0.4-15.9% for the TDx assay. Total imprecision (CV) averaged 6.2%, and within-run imprecision averaged 4.9%. Passing-Bablok linear regression analyses of all samples from two sites yielded the following: RxL = 0.81 x TDx - 16.8; and RxL = 1.12 x HPLC - 1.7.


CONCLUSIONS
The Dade Behring CsA assay for the random-access Dimension platform offers adequate performance characteristics for routine clinical use, does not require a manual pretreatment step, and demonstrates less cross-reactivity with CsA metabolites than another commonly used immunoassay.
Terrell
Andrea R
AR
Division of Laboratory Medicine, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110-1093, USA.
Daly
Thomas M
TM
Hock
Karl G
KG
Kilgore
Daniel C
DC
Wei
Tie Q
TQ
Hernandez
Sharon
S
Weibe
Don
D
Fields
Leona
L
Shaw
Leslie M
LM
Scott
Mitchell G
MG
D000911:Antibodies, Monoclonal; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions; D016572:Cyclosporine / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007166:Immunosuppressive Agents / Q000097:blood*; D016377:Organ Transplantation; D011933:Reagent Kits, Diagnostic
D000911:Antibodies, Monoclonal; D007166:Immunosuppressive Agents; D011933:Reagent Kits, Diagnostic; D016572:Cyclosporine