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Verification of EMIT method for measuring anticonvulsants concentrations on DxC 700 AU analyser

Introduction: The aim of our study was to examine precision and measurement uncertainty of EMIT method (enzyme-multiplied immunoassay technique) for measuring the concentration of carbamazepine, phenobarbitone and valproate in serum sample on DxC 700 AU analyser (Beckman Coulter, Brea, USA). Trueness of measured values were determined according to the manufacturer’s declared values of control material. Materials and methods: The verification was performed according to EP15-A2 CLSI verification protocol, using two levels of MAS ChemTRAK·H control material (Thermo Fisher Scientific, Waltham, USA) in triplicate during 5 days. The verification included determination of within-run precision (repeatability), between-run precision, intra-laboratory precision and trueness (bias). Measurement uncertainty was calculated from interlaboratory precision (k= 2) and compared with external quality assessment criteria, Croqalm (20%). The RiliBäk criteria (valproate 11.5%, carbamazepine 12%, phenobarbitone 10%) were used to estimate bias (%). Results: Coefficients of variation for within-run precision (CV%r) were 5.66 and 2.57 for carbamazepine, 1.74 and 2.44 for phenobarbitone and 1.43 and 1.57 for valproate. Between-run precision was (CV%b): 4.44 and 6.00 for carbamazepine, 2.65 and 2.37 for phenobarbitone and 1.43 and 1.57 for valproate. Measurement uncertainty (U%rel) from the data obtained by the verification procedure fulfilled the criteria of external quality assessment, and it was 12.81 and 12.71 for carbamazepine, 6.00 and 6.20 for phenobarbitone, and 5.62 and 5.87 for valproate. The obtained bias (%) was the highest for carbamazepine (9.48 and 12.82), 7.17 and 6.05 for phenobarbitone, and 7.41 and 7.78 for valproate. Conclusion: Verification of the EMIT method for the determination of carbamazepine, phenobarbitone and valproate met the criteria of external quality assessment, Croqalm in the assessment of measurement uncertainty. The obtained deviations for trueness regarding the manufacturer’s declared values of control material confirm the manufacturer’s recommendation that each laboratory has to check/ determine its own target values.

Verification ; carbamazepine ; phenobarbitone ; valproate

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