Internal Quality Control Evaluation of Therapeutic Drug Monitoring of Lamotrigine by Westgard Multi-rule Theory

OBJECTIVE To establish an internal quality control method for therapeutic drug monitoring of lamotrigine (LTG) and evaluate it by Westgard multi-rule theory. METHODS Self-made LTG quality control products with high, medium and low concentration(10, 5, 1 μg·mL^-1) were prepared. HPLC-UV was applied to determine the concentrations of 30 groups of self-made different quality control products from October to December 2018 under specified experimental conditions. The control charts of Levey-Jennings quality and Z-score were generated by Excel, and Westgard multi-rules were also used for quality assessment. RESULTS The intra-day and inter-day RSDs of low, medium and high concentration of LTG quality control products were 2.33%-9.62%, 5.63%-9.07%, respectively, while the extraction recovery rates were 70.48%-78.92%, 74.68%-80.77%, respectively. This meets the requirements of Chinese Pharmacopoeia for the detection of biological samples. Quality control charts of Levey-Jennings and Z-score showed that the results of 30 groups of self-made quality control products' concentration had violated Westgard multi-rule theory with one warning(violation of 1_2s rule) and one out of control(violation of 2_2s rule). After analysis, it was related to the long storage time of LTG working liquid and the monitoring data were returned to normal after reformulation. CONCLUSION The establishment of internal quality control system for therapeutic drug monitoring of LTG can effectively improve the accuracy of blood drug concentration monitoring, and provide more accurate clinical personalized pharmaceutical services.