IMPE Abstracts

Background: Inborn errors of metabolism (IEM) are a consequence of genetic defects that lead to a metabolic block in a biochemical pathway critical to tissue-specific cellular functions. Prompt and effective intervention in screening-positive patients is particularly important in cases of IEM. Newborn mass screening has developed aiming to identify newborns who appear healthy but who could be at risk of developing metabolic attacks with the potential to lead to serious complications or death. Newborn screening of IEM using tandem mass spectrometry has become a public health strategy in many developed countries. Retrospective analyses using stored dried blood specimens have been limited, mainly due to a lack of biochemical information on the long-term stability of acylcarnitines and amino acids in stored specimens. We studied the characteristic profiles of the stability of amino acid, free carnitine, and acylcarnitines in dried blood specimens stored in a refrigerator after newborn screening. Methods: Dried blood specimens from 198 healthy newborns that had been stored in a refrigerator at 5°C after newborn screening were prospectively subjected to tandem mass spectrometry analyses after 1, 3, 6 months, 1, 2 and 3 years of storage. We also retrospectively re-analyzed the stored samples from 90 newborns, which had been analyzed and stored at 5°C for 4 years. This study was approved by the ethics committee of Oita University Hospital (No. 1434). Results: We found that Pro and Tyr were stable for 3 years, and that Ala, Arg, Phe decayed with linear regression. The C0 increased during the time-course of 3 years, whereas most acylcarnitines gradually decayed and some showed a linear correlation. The retrospective analysis of samples stored for 4 years revealed that Ala, Phe, Pro and Tyr were almost stable, Leu, Val decayed with linear regression, C0 increased, and C10, C12, C14, C14:1, C16, C18, C18:1 decreased, while maintaining a linear correlation. Conclusions: These data suggested that a part of metabolic parameters from refrigerator-stored dried blood specimens were applicable for the detection of inborn errors of metabolism.