Abstract:Abstract: Objective:To evaluate the testing ability of the participating laboratories and improve the testing quality by carrying out the external quality assessment (EQA) for genetic testing of phenylketonuria. Methods:The 2019 EQA program was carried out twice a year, and 4 pathogenic variants on phenylalanine hydroxylase (PAH) gene, including missense variation and splicing variation, were investigated. A total of 5 different dry blood spot samples were detected each time. The participating laboratories were asked to detect the samples within the specified time after receiving the samples and report the test results online. According to the return results, the scores of each laboratory were calculated, the overall coincidences of different samples were summarized, and the detection results of the pathogenic variants and the types of error in the test reports were analyzed. Results:Three and two valid return results were received in the two EQA programs, respectively, and one and two laboratories achieved acceptable results, respectively. In the two EQA programs, the overall coincidence rates of detection results were 60% (9/15) and 100% (10/10), respectively. In the test reports, a total of 6 error results were presented, all of which were false negative. The coincidence rate of splicing variation was significantly lower than that of missense variation. Conclusion:The ability of clinical laboratories to detect the pathogenic variation of phenylketonuria and analyze the results should be improved. EQA program can help clinical laboratories find out the problems in testing and improve the quality of testing.