To the Editor
It is with great interest that we read the recent report by Spacil et al on a high-throughput assay to detect 9 lysosomal enzymes from dried blood spots (DBS) collected by newborn screening programs (Spacil Z, Tatipaka H, Barcenas M, Scott CR, Turecek F, Gelb MH. High-Throughput Assay of 9 Lysosomal Enzymes for Newborn Screening. Clin Chem 2013; 59: 502–511). Newborn screening activities to detect lysosomal storage disorders (NBS-LSD) have generated a great deal of discussion worldwide. The availability of tandem mass spectrometry (MS/MS)-based assays suitable for high-throughput population screening and of FDA-registered reagents for use in these assays led to an ongoing worldwide conversation about optimizing NBS-LSD assays. Recognizing the lack of DBS quality control materials (QC) for NBS-LSD, the Newborn Screening Translation Research Initiative (NSTRI) at the Centers for Disease Control and Prevention (CDC) developed large-scale methods to produce DBS that emulate normal and deficient lysosomal enzyme activities. The preparation and evaluation of these materials was originally reported in this journal (De Jesús VR, Zhang XK, Keutzer J, Bodamer OA, Mühl A, Orsini JJ, et al. Development and Evaluation of Quality Control Dried Blood Spot Materials in Newborn Screening for Lysosomal Storage Disorders. Clin Chem 2009; 55:158–164). These DBS-QC have been in use globally for over five years, and they were a critical element of the assay validation reported by Spacil et al. We want to be sure that Clinical Chemistry readers can locate the original article describing the DBS QC, which was not cited in their report.