Analytical performance evaluation of ADVIA Chemistry Carbamazepine_2 assay: minimal cross‐reactivity with carbamazepine 10, 11‐epoxide and none with hydroxyzine or cetirizine

Carbamazepine is an anticonvulsant requiring routine therapeutic drug monitoring. Recently, Siemens Healthcare Diagnostic Division released a new carbamazepine assay: ADVIA Chemistry Carbamazepine_2 (Carbamazepine_2) for application on ADVIA analyzers. We evaluated the analytical performance of this assay as well as its potential cross‐reactivities with carbamazepine 10, 11‐epoxide, hydroxyzine, and cetirizine. The within‐run and between‐run precisions of the Carbamzepine‐2 assay were <6% and limit of detection was 0.5 µg/ml using ADVIA 1800 analyzer. The assay was linear up to a carbamazepine concentration of 20.0 µg/ml. The new method compared well with a widely used carbamazepine EMIT 2000 assay on the Hitachi 917 analyzer. Using 75 patients' specimens (where carbamazepine concentrations varied from 0.5 to 21.7 µg/ml) and carbamazepine EMIT 2000 as the reference method ( x ‐axis), we observed the following regression equation: y =1.04 x +0.32 ( r =0.99). The new carbazepine_2 method was not affected by a hemoglobin concentration of 1,000 mg/dl, conjugated or unconjugated bilirubin concentration of 60 mg/dl, and triglyceride concentration of 1,000 mg/dl. In addition, this assay showed no cross‐reactivity with hydroxyzine or cetirizine and demonstrated minimal cross‐reactivity with carbamazepine 10, 11‐epoxide. We conclude that the ADVIA Chemistry carbamazepine_2 assay has adequate precision and accuracy for routine therapeutic drug monitoring of carbamazepine in clinical laboratories. J. Clin. Lab. Anal. 24:278–282, 2010. © 2010 Wiley‐Liss, Inc.