Butyrylcarnitine Elevation in Newborn Screening: Reducing False Positives and Distinguishing between Two Rare Diseases through the Evaluation of New Ratios

MariaAnna Messina; Alessia Arena; Riccardo Iacobacci; Luisa La Spina; Concetta Meli; Federica Raudino; Martino Ruggieri

doi:10.3390/biomedicines11123247

Butyrylcarnitine Elevation in Newborn Screening: Reducing False Positives and Distinguishing between Two Rare Diseases through the Evaluation of New Ratios

Biomedicines. 2023 Dec 7;11(12):3247. doi: 10.3390/biomedicines11123247.

Authors

MariaAnna Messina¹, Alessia Arena¹, Riccardo Iacobacci¹, Luisa La Spina¹, Concetta Meli¹, Federica Raudino¹, Martino Ruggieri^{1

2}

Affiliations

¹ Expanded Newborn Screening Laboratory, Newborn Screening and Metabolic Diseases Unit, University-Polyclinic "G. Rodolico-San Marco", 95123 Catania, Italy.
² Unit of Clinical Pediatrics, Department of Clinical and Experimental Medicine, University of Catania, 95123 Catania, Italy.

Abstract

One of the main challenges of newborn screening programs, which screen for inherited metabolic disorders, is cutting down on false positives (FPs) in order to avoid family stresses, additional analyses, and unnecessary costs. False positives are partly caused by an insubstantial number of robust biomarkers in evaluations. Another challenge is how to distinguish between diseases which share the same primary marker and for which secondary biomarkers are just as highly desirable. Focusing on pathologies that involve butyrylcarnitine (C4) elevation, such as short-chain acylCoA dehydrogenase deficiency (SCADD) and isobutyrylCoA dehydrogenase deficiency (IBDD), we investigated the acylcarnitine profile of 121 newborns with a C4 increase to discover secondary markers to achieve two goals: reduce the FP rate and discriminate between the two rare diseases. Analyses were carried out using tandem mass spectrometry with whole blood samples spotted on filter paper. Seven new biomarkers (C4/C0, C4/C5, C4/C5DC\C6OH, C4/C6, C4/C8, C4/C14:1, C4/C16:1) were identified using a non-parametric ANOVA analysis. Then, the corresponding cut-off values were found and applied to the screening program. The seven new ratios were shown to be robust (p < 0.001 and p < 0.01, 0.0937 < ε² < 0.231) in discriminating between FP and IBDD patients, FP and SCADD patients, or SCADD and IBDD patients. Our results suggest that the new ratios are optimal indicators for identifying true positives, distinguishing between two rare diseases that share the same primary biomarker, improving the predictive positive value (PPV) and reducing the false positive rate (FPR).

Keywords: biomarkers; inherited disorders; newborn screening; tandem mass spectrometry.

Grants and funding

According to the law 167/16, Italian newborn screening program costs are financed by the Government. Resolution no. 41/2017 (GU n.150-06/29/2017)—National Health Fund.