Comment on Dijkstra et al. A False-Negative Newborn Screen for Tyrosinemia Type 1-Need for Re-Evaluation of Newborn Screening with Succinylacetone. 2023, , 66.

The assessment of newborn screening (NBS) algorithms' performance to ensure quality improvements is a continuous process: false-positive referrals can enable optimisations in the shorter term, but false-negative referrals are often only discovered many years after the screening has taken place [...

Important Lessons on Long-Term Stability of Amino Acids in Stored Dried Blood Spots.

Residual heel prick Dried Blood Spots (DBS) are valuable samples for retrospective investigation of inborn metabolic diseases (IMD) and biomarker analyses. Because many metabolites suffer time-dependent decay, we investigated the five-year stability of amino acids (AA) in residual heel prick DBS. In 2019/2020, we analyzed 23 AAs in 2170 residual heel prick DBS from the Dutch neonatal screening program, stored from 2013-2017 (one year at +4 °C and four years at room temperature), using liquid chromatography mass-spectrometry.

Assessment of carnitine excretion and its ratio to plasma free carnitine as a biomarker for primary carnitine deficiency in newborns.

In the Netherlands, newborns are referred by the newborn screening (NBS) Program when a low free carnitine (C0) concentration (<5 μmol/l) is detected in their NBS dried blood spot. This leads to ~85% false positive referrals who all need an invasive, expensive and lengthy evaluation. We investigated whether a ratio of urine C0 / plasma C0 (Ratio) can improve the follow-up protocol for primary carnitine deficiency (PCD).