Development and evaluation of dried blood spot quality control materials in newborn screening for inborn errors of metabolism.

The application of tandem mass spectrometry (MS/MS) for detecting inborn errors of metabolism (IEM) is an important achievement in newborn screening (NBS). A single blood spot provides information on about 60 metabolites and related ratios that enable the screening of approximately 50 different diseases. A major limitation of newborn screening for IEM is the lack of matrix-matched dried blood spot (DBS) quality control (QC) materials in clinical laboratories. Herein, we developed DBS QC materials for IEM and investigated their recovery, homogeneity, and stability. Four concentration levels of DBS materials were prepared by spiking 9 amino acids, 6 acylcarnitines, and succinylacetone into a hemoglobin solution, which was dialyzed prior to preparing DBS. Hemoglobin solutions containing the predetermined quantities of metabolites were spotted, dried, and packaged. Isotope-dilution mass spectrometry was employed to estimate the endogenous contents and validate the final concentrations of alanine (Ala), proline (Pro), valine (Val), leucine (Leu), ornithine (Orn), methionine (Met), phenylalanine (Phe), arginine (Arg), citrulline (Cit), carnitine (C0), acetylcarnitine (C2), glutarylcarnitine (C5DC), octanoylcarnitine (C8), decanoylcarnitine (C10), dodecanoylcarnitine (C12), and succinylacetone (SA). The recovery, homogeneity, and post-preparation short-term stability of the DBS materials were also evaluated using an MS/MS assay. The recovery for amino acids was 81.4%-121.7%, with the exception of 68.2% for Arg. The recovery for acylcarnitines and succinylacetone was 60.0%-97.9%. The homogeneity, evaluated as between-spot coefficient of variation (CV) for the multilevel DBS materials, was 4.4%-16.6% for amino acids and 3.3%-19.8% for acylcarnitines and succinylacetone. Furthermore, DBS materials stored at 4 °C showed minimal deviation over the 28-day evaluation period for all metabolites. Multilevel DBS QC materials based on a hemoglobin matrix for newborn screening of IEM were developed for the first time. These QC materials can be used to monitor the daily analytical performance and improve the technical proficiency in clinical laboratories.