Comparison between the immunoassay and high performance liquid chromatography for therapeutic monitoring of carbamazepine and phenytoine

Objective: To investigate the correlation of the immuno assay and chromatography method for quantitative measurement of two antiepileptic drugs (AED), carbamazepine (CBZ) and phenytoin (PHT) and determination of relation between the CBZ and it's metabolite carbamazepine 10,11-epoxide (CBZ-E). Additionally we investigated whether there is a difference in the determination of serum concentration of CBZ and PHT when measured in two different labs by high performance liquid chromatography (HPLC). Materials and methods: This study was carried out on 102 blood samples (72 CBZ and 30 PHT) collected from epileptic out patients. Plasma concentrations of CBZ and PHT were determined by validated HPLC (Shimadzu and Agilent) and the CEDIA-immunoassay method. Results: The correlations of serum concentrations of CBZ between CEDIA and HPLC1 and between CEDIA and HPLC2 were good (R=0.97 for both techniques). Even better correlation was found between concentrations of CBZ measured by the two HPLC systems (R=0.99). Similar, for PHT, we found good correlation between CEDIA and the two systems of HPLC (HPLC1 and HPLC2, R=0.98) and between the two systems of HPLC of R=0.98. The moderate correlation coefficient was found between serum concentrations of CBZ and its metabolite CBZ-E, measured in two labs by different HPLC (R=0.49 and 0.43, respectively; P<0.001). Conclusion: We observed good correlation for estimation of CBZ and PHT concentration obtained by means the immunoassay and two different HPLC. The possibility of measurement of CBZ-E could be advantage of chromatography in comparison with immunoassay.