External quality assessment (EQA) trials for newborn screening tests were conducted twice in 2022 and 2023. These included tests for congenital hypothyroidism, adrenal hyperplasia, and galactosemia, as well as tandem mass spectrometry-based screenings for conditions such as phenylketonuria, maple syrup urine disease, homocystinuria. Each trial involved the analysis of six dried blood spot specimens for each test item across 15 laboratories. The mean, standard deviation, median, minimum and maximum values, and cut-offs were determined for each analyte in the newborn screening tests. The proportion of correct answers was 93%–100%. Additionally, EQA trials for the analyses of methylmalonic acid, vanillylmandelic acid, homovanillic acid, catecholamines, metanephrines, amino acids, and organic acids were performed using three specimens per trial. A well-designed EQA program, combined with continuous education, can help improve the performance of newborn screening and metabolite testing.

Keywords: External quality assessment, Newborn screening, Tandem mass spectrometry, Amino acid, Organic acid, Metabolite