Neonatal Screening Tests for Inherited Metabolic Disorders using Tandem Mass Spectrometry: Experience of a Clinical Laboratory in Korea

ABSTRACT

BACKGROUND: The purpose of this study is to investigate the positive rates of screening tests for inherited metabolic disorders, set cutoff values, and report the actual status of internal quality controls in LabGenomics Clinical Laboratories by using LC-MS/MS system. METHODS: We use Agilent 1260 Infinity HPLC System (Agilent Technologies, USA) for liquid chromatography, and API 2000 (AB Sciex, Canada) for MS/MS system. We set up screening tests for 55 diseases, which include metabolic disorders of 25 amino acids, 16 organic acids, and 14 fatty acids. RESULTS: We determined the analyte cutoff values as 99.9 or 0.1 percentiles in 15,000 newborn samples. The total number of samples tested from January 2012 to September 2014 was 119,948; of these, 6,681 were repeated. Of the repeated samples, 713 were presumed to be positive in the screening tests. Repeat screening with newly obtained dried blood spot specimens was recommended for these 713 samples and 600 specimens were obtained. Thus, the recall rate was 0.5% (600/119,948) for all samples and 84.2% (600/713) for the samples presumed to be positive in the screening tests. About 70 samples, that is, 0.06% of the total samples and 11.7% of the "reobtained" samples, again tested positive; we recommended confirmatory tests for these samples. CONCLUSIONS: We have presented data on the status of neonatal screening tests for inherited metabolic disorders using LC-MS/MS, including positive rates and recall rates of screening tests, set up cutoff values and reported the actual status of internal quality controls in a clinical laboratory in Korea.