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

Abstract

We performed two trials on the external quality assessment for therapeutic drug monitoring (TDM) and testing for drugs of abuse (DOA) organized by the Therapeutic Drug Monitoring (TDM) subcommittee of the Korean Association of Quality Assurance for Clinical Laboratories (KAQACL) in 2013. In each trial, two levels of control material for TDM, and positive and negative control material for DOA testing, were requested from candidate institutions. The number of participating laboratories was 106 and 105 for the first and second trials, respectively. The average number of drug items was 5.6 per institution. The most commonly tested substances were valproic acid, followed by digoxin, phenytoin, carbamazepine, and tacrolimus, in descending order. The mean inter-laboratory coefficients of variation for low- and high-level control materials were 9.3% and 6.7%, respectively. The most widely used TDM analysers were Architect i System (Abbott Diagnostics, USA), followed by Cobas Integra (Roche Diagnostics, Switzerland) and Cobas c501 analyser (Roche Diagnostics). The number of participating laboratories for DOA testing increased by 30% compared with that in 2012. We received 100% and 98.2% correct answers from the participating DOA laboratories in each trial, respectively. In the external quality assessment for TDM by the TDM subcommittee of KAQACL in 2013, the overall performance of TDM was similar to previous years and the inter-laboratory precision was improved compared with that in 2012. Continuous quality improvement for TDM testing is needed through participation in a proficiency-testing program.