Results of a global external quality assessment scheme for EGFR testing on liquid biopsy

Background Cell free DNA (cfDNA) testing of EGFR mutations is widely employed in lung cancer patients. Liquid biopsy testing is highly challenging due to the low level of mutant DNA present with normal DNA. Therefore, cfDNA testing requires quality assessment to ensure patient safety. The international external quality assessment (EQA) provider consortium, IQNPath has delivered a second successful EQA run to determine the standard of cfDNA testing for EGFR mutations. Methods Five European EQA providers (AIOM, EMQN, ESP, Gen&Tiss, UKNEQAS), under the umbrella of IQNPath, collaborated to deliver the assessment during 2018-19 to a total of 310 laboratories from 44 countries. A panel of bespoke manufactured plasma samples with varying EGFR mutations at a range of allelic frequencies were validated by a range of methodologies prior to distribution to ensure stability and reproducibility. The EQA samples were supplied for testing and reporting according to laboratory routine protocols. Peer reviewed criteria was applied to assess the standard of genotyping and reporting. Results Of the 310 laboratories that had joined the program, 270 submitted the results within the established deadline. Preliminary analysis of the data submitted by participating laboratories showed that low allelic frequency samples were the most challenging and some methods did not detect these mutations. Reporting of such cases often did not address the risk that tumour DNA may have not been tested and limitations of the testing performed was not addressed when reporting the result. The final results of the EQA scheme will be presented at the meeting. Conclusions The variability in the standard of genotyping and reporting highlights the need for EQA in this field and educational guidance to ensure the delivery of high-quality clinical service where testing of cfDNA is the only option for clinical management. Legal entity responsible for the study IQNPath. Funding IQNPath. Disclosure All authors have declared no conflicts of interest.