Annual Report on the External Quality Assessment of Therapeutic Drug Monitoring and Testing for Drugs of Abuse in Korea (2013)

Dae-Hyun Ko, GumGyoung Gu, EunJung Cho, Eun Suk Shin, Sail Chun, and Jeong-Ho Kim, as Therapeutic Drug Monitoring Subcommittee, Korean Association of External Quality Assessment Service Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine; Department of Laboratory Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea As an annual function of the Therapeutic Drug Monitoring Subcommittee of Korean Association of External Quality Assessment Service (K-EQAS), we organised two trials for an external quality assessment of therapeutic drug monitoring (TDM) and testing for drugs of abuse (DOA) in 2015. For the TDM assessment, we sent lowand high-level control materials from various clinical institutions, and for the DOA testing, we sent positive and negative control materials. The number of participating laboratories was 105 for the TDM trial and 106 for the DOA test. The average number of drug items provided was 5.6 per institution. The most commonly tested substances, in descending order, were: valproic acid, digoxin, vancomycin, tacrolimus, and carbamazepine. The mean inter-laboratory coefficients of variation for lowand high-level TDM control materials were 7.3% and 7.4%, respectively. The most widely used TDM analysers were the Architect i System (Abbott Diagnostics, USA), followed by the Cobas Integra (Roche Diagnostics, Switzerland) and the Cobas c501 analyser (Roche Diagnostics). The number of participating laboratories for the DOA analysis was 16% higher that than of our 2014 study. In 98.6% of cases, our analysis confirmed the reliabilityviability of the tests at participating DOA laboratories in both trials. In the external quality assessment of TDM by the TDM subcommittee of K-EQAS in 2015, the overall performance of TDM testing was found to be similar to that reported in previous years, and inter-laboratory precision was higher than that of 2014. Continuous improvement in the quality of TDM testing through participation in a proficiency-testing program will remain necessary in the future. (J Lab Med Qual Assur 2016;38:11-21)