Comparison of the QMS® analyzer with HPLC-UV for the quantification of lamotrigine concentrations in human plasma samples

Background: Recently, a turbidimetric immunoassay method has been developed for use in the form of a QMS lamotrigine (LTG) commercial immunoassay. This study was designed to evaluate the performance of this immunoassay using a validated highperformance liquid chromatography-ultraviolet (HPLC-UV) method as the reference. Methods: The performance of QMS was initially tested using drugfree plasma spiked with different amounts of LTG and, subsequently, by analyzing 61 trough plasma samples from epileptic patients given the drug as part of their maintenance antiepileptic therapies. Results: The correlation between LTG concentrations measured by QMS and HPLC was good, with a Pearson coefficient of 0.968 (P < 0.0001). The Bland-Altman approach showed that LTG concentrations measured with QMS exceeded HPLC on an average by 15.6% (limits of agreement, -18% to +63%), with a concentrationdependent performance (mean percent bias, 49.5 ± 8.2% and 0.6 ± 12.7% for concentrations less than 2 mg/L and greater than 14.9 mg/L, respectively). Conclusions: The QMS provided acceptable analytical performance across a wide concentration range for routine LTG measurements, being at least comparable with the other commercial immunoassays. It could be, therefore, considered as a viable alternative to HPLC methods for routine LTG monitoring in the clinical practice, although its suitability for accurate analysis of samples with low concentration is limited.