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Lin Y, Zheng Z, Lin W, Peng W. Incorporating Next-Generation Sequencing as a Second-Tier Test for Primary Carnitine Deficiency. Mol Genet Genomic Med 2024; 12:e70003. [PMID: 39248612 PMCID: PMC11382357 DOI: 10.1002/mgg3.70003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 07/21/2024] [Accepted: 08/13/2024] [Indexed: 09/10/2024] Open
Abstract
BACKGROUND Newborn screening (NBS) for primary carnitine deficiency (PCD) has poor performance. This study aimed to evaluate the feasibility of incorporating next-generation sequencing (NGS) as a second-tier PCD test. METHODS Between March and December 2020, 60,070 newborns were screened for inherited metabolic disorders. Newborns with free carnitine (C0) levels below 8.5 μmol/L were selected for second-tier genetic testing. RESULTS In total, 130 (0.22%) newborns with low C0 levels underwent second-tier genetic testing, 87 (66.92%) had positive genetic testing results, and 30 (23.08%) carried pathogenic variants of the SLC22A5 gene. Six newborns were diagnosed with PCD. The incidence of PCD was approximately 1 in 1:10,012 newborns. The PPV reached 20% after combining with second-tier NGS. Of the eight variants identified in patients with PCD, the three most common variants were c.760C>T (p.Arg254*), c.51C>G (p.Phe17Leu), and c.1400C>G (p.Ser467Cys). The C0 levels of patients with PCD were significantly lower than those of PCD carriers (p = 0.0026) and PCD-negative individuals (p = 0.0005). CONCLUSIONS Our results showed that the PPV reached 20% after combining with second-tier NGS. The MS/MS-based NBS and second-tier NGS combination can effectively reduce the false-positive rate and detect PCD in patients.
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Affiliation(s)
- Yiming Lin
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian, China
| | - Zhenzhu Zheng
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian, China
| | - Weihua Lin
- Neonatal Disease Screening Center, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian, China
| | - Weilin Peng
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian, China
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2
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Lin Y, Lin C, Zheng Z, Huang C, Peng W. Newborn screening for primary carnitine deficiency using a second-tier genetic test. J Pediatr Endocrinol Metab 2024; 37:163-169. [PMID: 38158618 DOI: 10.1515/jpem-2023-0513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 12/18/2023] [Indexed: 01/03/2024]
Abstract
OBJECTIVES Newborn screening (NBS) for primary carnitine deficiency (PCD) exhibits suboptimal performance. This study proposes a strategy to enhance the efficacy of second-tier genetic screening by adjusting the cutoff value for free carnitine (C0). METHODS Between January 2021 and December 2022, we screened 119,898 neonates for inborn metabolic disorders. Neonates with C0 levels below 12 μmol/L were randomly selected for second-tier genetic screening, employing a novel matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) assay. RESULTS In total, 2,515 neonates with C0 <12 μmol/L underwent further screening, including 206 neonates with C0 <8.5 μmol/L and 320 neonates with 8.5G, accounting for 25 % (7/28) of allelic frequencies. CONCLUSIONS A novel MALDI-TOF MS assay targeting 21 SLC22A5 variants in a Chinese population was successfully established. This assay exhibits a high detection and diagnostic rate, making it suitable for population-based genetic screening. Combined genetic screening is recommended to enhance the efficiency of PCD-NBS.
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Affiliation(s)
- Yiming Lin
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian Province, P.R. China
| | - Chunmei Lin
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian Province, P.R. China
| | - Zhenzhu Zheng
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian Province, P.R. China
| | - Chenggang Huang
- Zhejiang Biosan Biochemical Technologies Co., Ltd., Hangzhou, Zhejiang Province, P.R. China
| | - Weilin Peng
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, Quanzhou, Fujian Province, P.R. China
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3
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Lin Y, Lin C, Lin B, Zheng Z, Lin W, Chen Y, Chen D, Peng W. Newborn screening for fatty acid oxidation disorders in a southern Chinese population. Heliyon 2024; 10:e23671. [PMID: 38187300 PMCID: PMC10770602 DOI: 10.1016/j.heliyon.2023.e23671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 11/23/2023] [Accepted: 12/09/2023] [Indexed: 01/09/2024] Open
Abstract
Background and aims Fatty acid oxidation disorders (FAODs) are a group of autosomal recessive metabolic diseases included in many newborn screening (NBS) programs, but the incidence and disease spectrum vary widely between ethnic groups. We aimed to elucidate the incidence, disease spectrum, and genetic features of FAODs in a southern Chinese population. Materials and methods The FAODs screening results of 643,606 newborns from 2014 to 2022 were analyzed. Results Ninety-two patients were eventually diagnosed with FAODs, of which 61 were PCD, 20 were MADD, 5 were SCADD, 4 were VLCADD, and 2 were CPT-IAD. The overall incidence of FAODs was 1:6996 (95 % CI: 1:5814-1:8772) newborns. All PCD patients had low C0 levels during NBS, while nine patients (14.8 %) had normal C0 levels during the recall review. All but one MADD patients had elevated C8, C10, and C12 levels during NBS, while eight patients (40 %) had normal acylcarnitine levels during the recall review. The most frequent SLC22A5 variant was c.760C > T (p.R254*) with an allele frequency of 29.51 %, followed by c.51C > G (p.F17L) (17.21 %) and c.1400C > G (p.S467C) (16.39 %). The most frequent ETFDH variant was c.250G > A (p.A84T) with an allelic frequency of 47.5 %, followed by c.524G > A (R175H) (12.5 %), c.998A > G (p.Y333C) (12.5 %), and c.1657T > C (p.Y553H) (7.5 %). Conclusion The prevalence, disease spectrum, and genetic characteristics of FAODs in a southern Chinese population were clarified. PCD was the most common FAOD, followed by MADD. Hotspot variants were found in SLC22A5 and ETFDH genes, while the remaining FAODs showed great molecular heterogeneity. Incorporating second-tier genetic screening is critical for FAODs.
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Affiliation(s)
- Yiming Lin
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Chunmei Lin
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Bangbang Lin
- Administrative office, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Zhenzhu Zheng
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Weihua Lin
- Center of Neonatal Disease Screening, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Yanru Chen
- Center of Neonatal Disease Screening, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Dongmei Chen
- Department of Neonatology, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
| | - Weilin Peng
- Department of Clinical Laboratory, Quanzhou Maternity and Children's Hospital, 700 Fengze Street, Quanzhou, Fujian Province, 362000, China
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4
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Maier EM, Mütze U, Janzen N, Steuerwald U, Nennstiel U, Odenwald B, Schuhmann E, Lotz-Havla AS, Weiss KJ, Hammersen J, Weigel C, Thimm E, Grünert SC, Hennermann JB, Freisinger P, Krämer J, Das AM, Illsinger S, Gramer G, Fang-Hoffmann J, Garbade SF, Okun JG, Hoffmann GF, Kölker S, Röschinger W. Collaborative evaluation study on 18 candidate diseases for newborn screening in 1.77 million samples. J Inherit Metab Dis 2023; 46:1043-1062. [PMID: 37603033 DOI: 10.1002/jimd.12671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 08/16/2023] [Accepted: 08/17/2023] [Indexed: 08/22/2023]
Abstract
Analytical and therapeutic innovations led to a continuous but variable extension of newborn screening (NBS) programmes worldwide. Every extension requires a careful evaluation of feasibility, diagnostic (process) quality and possible health benefits to balance benefits and limitations. The aim of this study was to evaluate the suitability of 18 candidate diseases for inclusion in NBS programmes. Utilising tandem mass spectrometry as well as establishing specific diagnostic pathways with second-tier analyses, three German NBS centres designed and conducted an evaluation study for 18 candidate diseases, all of them inherited metabolic diseases. In total, 1 777 264 NBS samples were analysed. Overall, 441 positive NBS results were reported resulting in 68 confirmed diagnoses, 373 false-positive cases and an estimated cumulative prevalence of approximately 1 in 26 000 newborns. The positive predictive value ranged from 0.07 (carnitine transporter defect) to 0.67 (HMG-CoA lyase deficiency). Three individuals were missed and 14 individuals (21%) developed symptoms before the positive NBS results were reported. The majority of tested candidate diseases were found to be suitable for inclusion in NBS programmes, while multiple acyl-CoA dehydrogenase deficiency, isolated methylmalonic acidurias, propionic acidemia and malonyl-CoA decarboxylase deficiency showed some and carnitine transporter defect significant limitations. Evaluation studies are an important tool to assess the potential benefits and limitations of expanding NBS programmes to new diseases.
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Affiliation(s)
- Esther M Maier
- Department of Inborn Errors of Metabolism, Dr. von Hauner Children's Hospital, Munich, Germany
| | - Ulrike Mütze
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Nils Janzen
- Screening-Labor Hanover, Hanover, Germany
- Department of Clinical Chemistry, Hanover Medical School, Hanover, Germany
- Division of Laboratory Medicine, Centre for Children and Adolescents, Kinder- und Jugendkrankenhaus Auf der Bult, Hanover, Germany
| | | | - Uta Nennstiel
- Bavarian Health and Food Safety Authority, Oberschleissheim, Germany
| | - Birgit Odenwald
- Bavarian Health and Food Safety Authority, Oberschleissheim, Germany
| | | | - Amelie S Lotz-Havla
- Department of Inborn Errors of Metabolism, Dr. von Hauner Children's Hospital, Munich, Germany
| | - Katharina J Weiss
- Department of Inborn Errors of Metabolism, Dr. von Hauner Children's Hospital, Munich, Germany
| | - Johanna Hammersen
- Department of Pediatrics, Division of Inborn Errors of Metabolism, University Hospital Erlangen, Erlangen, Germany
| | - Corina Weigel
- Department of Pediatrics, Division of Inborn Errors of Metabolism, University Hospital Erlangen, Erlangen, Germany
| | - Eva Thimm
- Department of General Pediatrics, University Children's Hospital, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Sarah C Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Centre-University of Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Julia B Hennermann
- Villa Metabolica, Center for Pediatric and Adolescent Medicine, Mainz University Medical Center, Mainz, Germany
| | - Peter Freisinger
- Children's Hospital Reutlingen, Klinikum am Steinenberg, Reutlingen, Germany
| | - Johannes Krämer
- Department of Pediatric and Adolescent Medicine, Ulm University Medical School, Ulm, Germany
| | - Anibh M Das
- Hanover Medical School, Clinic for Pediatric Kidney-Liver- and Metabolic Diseases, Hanover, Germany
| | - Sabine Illsinger
- Hanover Medical School, Clinic for Pediatric Kidney-Liver- and Metabolic Diseases, Hanover, Germany
| | - Gwendolyn Gramer
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
- University Medical Center Hamburg-Eppendorf, University Children's Hospital, Hamburg, Germany
| | - Junmin Fang-Hoffmann
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Sven F Garbade
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Jürgen G Okun
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Georg F Hoffmann
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Stefan Kölker
- Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Wulf Röschinger
- Laboratory Becker MVZ GbR, Newborn Screening Unit, Munich, Germany
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5
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van den Heuvel LM, Kater-Kuipers A, van Dijk T, Crefcoeur LL, Visser G, Langeveld M, Henneman L. A qualitative study on the perspectives of mothers who had been diagnosed with primary carnitine deficiency through newborn screening of their child. Orphanet J Rare Dis 2023; 18:134. [PMID: 37268964 DOI: 10.1186/s13023-023-02735-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 05/14/2023] [Indexed: 06/04/2023] Open
Abstract
BACKGROUND Primary carnitine deficiency is an inborn error of metabolism, which can lead to life-threating complications early in life. Low carnitine levels can be detected by newborn bloodspot screening (NBS). However, NBS can also identify, mostly asymptomatic, mothers with primary carnitine deficiency. To identify mothers' needs and areas for improving screening practice, this study explored the experiences with, and opinions on primary carnitine deficiency screening in NBS among women diagnosed through NBS of their newborn. METHODS Twelve Dutch women were interviewed, 3-11 years after diagnosis. Data were analysed using a thematic approach. RESULTS Four main themes were derived: 1) psychological impact of primary carnitine deficiency diagnosis, 2) becoming a patient and "patient-in-waiting", 3) information issues and care provision, and 4) primary carnitine deficiency as part of the NBS panel. Mothers shared that they did not experience major psychological distress of the diagnosis. They did experience (recall) various emotions following the initial abnormal NBS result, including fear and anxiety as well as relief, and emotions regarding their own diagnosis, including uncertainty about health risks and treatment effectiveness. Some felt a patient-in-waiting. Many participants experienced a lack of information, especially shortly after receiving the abnormal NBS result. All shared the belief that screening for primary carnitine deficiency in NBS is beneficial for the newborn, and, given the information they received, also considered the knowledge beneficial for their own health. CONCLUSIONS Psychological burden following diagnosis was experienced by women as limited, although the experienced lack of information amplified feelings of uncertainty and anxiety. Most mothers believed that benefits of knowing about primary carnitine deficiency outweighed the disadvantages. Mothers' perspectives should be incorporated in policy-making about primary carnitine deficiency in NBS.
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Affiliation(s)
- Lieke M van den Heuvel
- Department of Human Genetics, Amsterdam UMC, location Vrije Universiteit, Amsterdam, the Netherlands
- Amsterdam Reproduction and Development research institute, Amsterdam, the Netherlands
| | - Adriana Kater-Kuipers
- Department of Human Genetics, Amsterdam UMC, location Vrije Universiteit, Amsterdam, the Netherlands
- Amsterdam Reproduction and Development research institute, Amsterdam, the Netherlands
| | - Tessa van Dijk
- Department of Human Genetics, Amsterdam UMC, location Vrije Universiteit, Amsterdam, the Netherlands
- Amsterdam Reproduction and Development research institute, Amsterdam, the Netherlands
| | - Loek L Crefcoeur
- Wilhelmina Children's Hospital, Section Metabolic Diseases, University Medical Centre Utrecht, Utrecht, the Netherlands
| | - Gepke Visser
- Wilhelmina Children's Hospital, Section Metabolic Diseases, University Medical Centre Utrecht, Utrecht, the Netherlands
| | - Mirjam Langeveld
- Department of Endocrinology and Metabolism, Amsterdam UMC, location University of Amsterdam, Amsterdam, the Netherlands
| | - Lidewij Henneman
- Department of Human Genetics, Amsterdam UMC, location Vrije Universiteit, Amsterdam, the Netherlands.
- Amsterdam Reproduction and Development research institute, Amsterdam, the Netherlands.
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6
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Lefèvre CR, Labarthe F, Dufour D, Moreau C, Faoucher M, Rollier P, Arnoux JB, Tardieu M, Damaj L, Bendavid C, Dessein AF, Acquaviva-Bourdain C, Cheillan D. Newborn Screening of Primary Carnitine Deficiency: An Overview of Worldwide Practices and Pitfalls to Define an Algorithm before Expansion of Newborn Screening in France. Int J Neonatal Screen 2023; 9:6. [PMID: 36810318 PMCID: PMC9944086 DOI: 10.3390/ijns9010006] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 01/24/2023] [Accepted: 01/28/2023] [Indexed: 02/04/2023] Open
Abstract
Primary Carnitine Deficiency (PCD) is a fatty acid oxidation disorder that will be included in the expansion of the French newborn screening (NBS) program at the beginning of 2023. This disease is of high complexity to screen, due to its pathophysiology and wide clinical spectrum. To date, few countries screen newborns for PCD and struggle with high false positive rates. Some have even removed PCD from their screening programs. To understand the risks and pitfalls of implementing PCD to the newborn screening program, we reviewed and analyzed the literature to identify hurdles and benefits from the experiences of countries already screening this inborn error of metabolism. In this study, we therefore, present the main pitfalls encountered and a worldwide overview of current practices in PCD newborn screening. In addition, we address the optimized screening algorithm that has been determined in France for the implementation of this new condition.
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Affiliation(s)
| | - François Labarthe
- Reference Center of Inherited Metabolic Disorders, Clocheville Hospital, 37000 Tours, France
| | - Diane Dufour
- Reference Center of Inherited Metabolic Disorders, Clocheville Hospital, 37000 Tours, France
| | | | | | - Paul Rollier
- Rennes University Hospital Center, 35033 Rennes, France
| | - Jean-Baptiste Arnoux
- Reference Center for Inborn Error of Metabolism, Department of Pediatrics, Necker-Enfants Malades Hospital, APHP, 75015 Paris, France
| | - Marine Tardieu
- Reference Center of Inherited Metabolic Disorders, Clocheville Hospital, 37000 Tours, France
| | - Léna Damaj
- Rennes University Hospital Center, 35033 Rennes, France
| | | | - Anne-Frédérique Dessein
- Metabolism and Rare Disease Unit, Department of Biochemistry and Molecular Biology, Center of Biology and Pathology, Lille University Hospital Center, 59000 Lille, France
| | - Cécile Acquaviva-Bourdain
- Center for Inherited Metabolic Disorders and Neonatal Screening, East Biology and Pathology Department, Groupement Hospitalier Est (GHE), Hospices Civils de Lyon, 69500 Bron, France
| | - David Cheillan
- Center for Inherited Metabolic Disorders and Neonatal Screening, East Biology and Pathology Department, Groupement Hospitalier Est (GHE), Hospices Civils de Lyon, 69500 Bron, France
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7
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Louis L, Margaux G, Claire G, Delphine L, Sandrine R, Emmanuel R, Cécile G, Samir M, Isabelle R. Infantile primary carnitine deficiency: A severe cardiac presentation unresponsive to carnitine supplementation. JIMD Rep 2023; 64:35-41. [PMID: 36636599 PMCID: PMC9830015 DOI: 10.1002/jmd2.12346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 10/11/2022] [Accepted: 10/21/2022] [Indexed: 11/11/2022] Open
Abstract
Primary carnitine deficiency (PCD) is an inherited disease of fatty acid beta-oxidation with autosomal recessive inheritance. The disease manifests as metabolic decompensation with hypoketotic hypoglycaemia associated with cardiomyopathy, hepatomegaly, rhabdomyolysis, and seizures. Various outcomes are described from asymptomatic adults to dramatic sudden infant death syndrome cases. We present a severe case of PCD decompensation in an 18-week-old female. She presented with hypotonia, moaning, diarrhea, and vomiting at the pediatric emergency. Initially suspected as intracranial hypertension, the clinical condition evolved rapidly and caused a reversible cardiac arrest with profound hypoglycemia. Despite carnitine supplementation, she succumbed from cardiac arrhythmia and multivisceral failure 4 days after admission. The genetic analyses showed a PCD with biallelic pathogenic variants of SLC22A5 gene. The case report is notable for the severity of the cardiac damage possibly favored by maternal carnitine deficiency during pregnancy. The analysis of previously published PCD cases highlights (i) the importance of having large access to emergency biochemical tests for early therapeutic care although the disease has unpredictable severity and (ii) the fact that the clinical outcome remains unpredictable if carnitine treatment is initiated late.
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Affiliation(s)
- Lebreton Louis
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
| | | | - Guibet Claire
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
| | - Lamireau Delphine
- Hôpital Pédiatrique, Pôle Pédiatrique, CHU de BordeauxBordeauxFrance
| | - Roche Sandrine
- Hôpital Pédiatrique, Pôle Pédiatrique, CHU de BordeauxBordeauxFrance
| | - Richard Emmanuel
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
- INSERM BRIC U1312Université de BordeauxBordeauxFrance
| | - Ged Cécile
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
- INSERM BRIC U1312Université de BordeauxBordeauxFrance
| | - Mesli Samir
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
| | - Redonnet‐Vernhet Isabelle
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
- lNSERM MRGM U1211Université de BordeauxBordeauxFrance
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8
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Crefcoeur LL, Heiner‐Fokkema MR, Maase RE, Visser G, de Sain‐van der Velden MGM. Assessment of carnitine excretion and its ratio to plasma free carnitine as a biomarker for primary carnitine deficiency in newborns. JIMD Rep 2023; 64:57-64. [PMID: 36636597 PMCID: PMC9830017 DOI: 10.1002/jmd2.12334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 08/31/2022] [Indexed: 01/16/2023] Open
Abstract
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 (RatioU:P) can improve the follow-up protocol for primary carnitine deficiency (PCD). A retrospective study was performed in all Dutch metabolic centres, using samples from newborns and mothers referred by NBS due to low C0 concentration. Samples were included when C0 excretion and plasma C0 concentration were sampled on the same day. RatioU:P was calculated as (urine C0 [μmol/mmol creatinine])/(plasma C0 [μmol/l]). Data were available for 59 patients with genetically confirmed PCD and 68 individuals without PCD. The RatioU:P in PCD patients was significantly higher (p value < 0.001) than in those without PCD, median [IQR], respectively: 3.4 [1.2-9.5], 0.4 [0.3-0.8], area under the curve (AUC) 0.837. Classified for age (up to 1 month) and without carnitine suppletion (PCD; N = 12, Non-PCD; N = 40), medians were 6.20 [4.4-8.8] and 0.37 [0.24-0.56], respectively. The AUC for RatioU:P was 0.996 with a cut-off required for 100% sensitivity at 1.7 (yielding one false positive case). RatioU:P accurately discriminates between positive and false positive newborn referrals for PCD by NBS. RatioU:P is less effective as a discriminative tool for PCD in adults and for individuals that receive carnitine suppletion.
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Affiliation(s)
- Loek L. Crefcoeur
- Department of Metabolic Diseases, Wilhelmina Children's HospitalUniversity Medical Center UtrechtUtrechtThe Netherlands
- Division of Metabolic Diseases, Amsterdam Gastroenterology and Metabolism, Emma Children's HospitalAmsterdam UMC, Location University of AmsterdamAmsterdamThe Netherlands
| | - M. Rebecca Heiner‐Fokkema
- Department of Laboratory MedicineUniversity of Groningen, University Medical Center GroningenGroningenThe Netherlands
| | - Rose E. Maase
- Department Biologicals, Screening and InnovationDutch National Institute for Public Health and the EnvironmentBilthovenThe Netherlands
| | - Gepke Visser
- Department of Metabolic Diseases, Wilhelmina Children's HospitalUniversity Medical Center UtrechtUtrechtThe Netherlands
- Division of Metabolic Diseases, Amsterdam Gastroenterology and Metabolism, Emma Children's HospitalAmsterdam UMC, Location University of AmsterdamAmsterdamThe Netherlands
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9
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Koleske ML, McInnes G, Brown JEH, Thomas N, Hutchinson K, Chin MY, Koehl A, Arkin MR, Schlessinger A, Gallagher RC, Song YS, Altman RB, Giacomini KM. Functional genomics of OCTN2 variants informs protein-specific variant effect predictor for Carnitine Transporter Deficiency. Proc Natl Acad Sci U S A 2022; 119:e2210247119. [PMID: 36343260 PMCID: PMC9674959 DOI: 10.1073/pnas.2210247119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 09/16/2022] [Indexed: 11/09/2022] Open
Abstract
Genetic variants in SLC22A5, encoding the membrane carnitine transporter OCTN2, cause the rare metabolic disorder Carnitine Transporter Deficiency (CTD). CTD is potentially lethal but actionable if detected early, with confirmatory diagnosis involving sequencing of SLC22A5. Interpretation of missense variants of uncertain significance (VUSs) is a major challenge. In this study, we sought to characterize the largest set to date (n = 150) of OCTN2 variants identified in diverse ancestral populations, with the goals of furthering our understanding of the mechanisms leading to OCTN2 loss-of-function (LOF) and creating a protein-specific variant effect prediction model for OCTN2 function. Uptake assays with 14C-carnitine revealed that 105 variants (70%) significantly reduced transport of carnitine compared to wild-type OCTN2, and 37 variants (25%) severely reduced function to less than 20%. All ancestral populations harbored LOF variants; 62% of green fluorescent protein (GFP)-tagged variants impaired OCTN2 localization to the plasma membrane of human embryonic kidney (HEK293T) cells, and subcellular localization significantly associated with function, revealing a major LOF mechanism of interest for CTD. With these data, we trained a model to classify variants as functional (>20% function) or LOF (<20% function). Our model outperformed existing state-of-the-art methods as evaluated by multiple performance metrics, with mean area under the receiver operating characteristic curve (AUROC) of 0.895 ± 0.025. In summary, in this study we generated a rich dataset of OCTN2 variant function and localization, revealed important disease-causing mechanisms, and improved upon machine learning-based prediction of OCTN2 variant function to aid in variant interpretation in the diagnosis and treatment of CTD.
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Affiliation(s)
- Megan L. Koleske
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94143
| | - Gregory McInnes
- Biomedical Informatics Training Program, Stanford University, Stanford, CA 94305
- Empirico Inc., San Diego, CA 92122
| | - Julia E. H. Brown
- Program in Bioethics, University of California, San Francisco, CA 94143
- Institute for Health & Aging, University of California, San Francisco, CA 94143
| | - Neil Thomas
- Computer Science Division, University of California, Berkeley, CA 94720
| | - Keino Hutchinson
- Department of Pharmacological Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY 10029
| | - Marcus Y. Chin
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143
| | - Antoine Koehl
- Department of Statistics, University of California, Berkeley, CA 94720
| | - Michelle R. Arkin
- Small Molecule Discovery Center, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY 10029
| | - Renata C. Gallagher
- Institute for Human Genetics, University of California, San Francisco, CA 94143
- Department of Pediatrics, University of California, San Francisco, CA 94143
| | - Yun S. Song
- Computer Science Division, University of California, Berkeley, CA 94720
- Department of Statistics, University of California, Berkeley, CA 94720
| | - Russ B. Altman
- Department of Bioengineering, Stanford University, Stanford, CA 94305
- Department of Genetics, Stanford University, Stanford, CA 94305
| | - Kathleen M. Giacomini
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94143
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