Selective Screening for Inborn Errors of Metabolism: A Report of Six Years Experience

Background: Tandem MS analysis of dried blood spots is a widely used method for diagnosis of inborn errors of metabolism. Clinical laboratories performing this test for clinically suspected children at different ages are faced with the challenge of using appropriate reference ranges for the diagnostic markers. Objectives: Retrospective evaluation of laboratory data was performed to establish the disease spectrum and clinically relevant reference ranges for the diagnostic markers. Methods: The results of clinically suspected 4800 patients were extracted from laboratory information system and correlated with clinical data. Relevant reference ranges for the analytes in dried blood spots was determined using nonparametric statistical methods. Results: Forty four patients were diagnosed with 12 different inborn errors of metabolism. There were 23 patients with organic acid disorder, 13 patients with amino acid or urea cycle disorder and 8 patients with fatty acid oxidation disorder. The reference ranges were significantly different between the children under and over 1 year of age for some acylcarnitines (C0, C2, C3, C5OH, C14, C16 and C18) and amino acids (citrulline, arginine, tyrosine, valine and leucine). Conclusions: The interpretation of the Tandem MS analysis results showed that the difference in the reference ranges for children under or over one year of age did not affect the diagnosis for most frequent inborn errors of metabolism.