25 Years of Newborn Screening in Uruguay

Abstract In the 1960s Guthrie conceived the idea of preventing congenital disease using dried blood spot samples on filter paper to detect them through biochemical tests and then be able to treat environmental factors in time to avoid the devastating effect of the diseases. Uruguay started in 1994 with the detection of congenital hypothyroidism in umbilical cord blood. In 2007 it was extended to Phenylketonuria and Congenital Adrenal Hyperplasia, starting with dried blood spot sample. In 2008, with the incorporation of Mass Spectrometry, a pilot program was started for the detection of aminoacidopathies, beta-oxidation defects and organic acidemias disorders. In the following years, the program expanded to more diseases, reaching a total of 25 disorders that could be detected, 5 of them are investigated on a mandatory basis and others in pilot program. During the 25-year of experience, 974277 umbilical cord blood samples were analyzed and since 2007: 532684 dried blood spot samples. 613 true positive congenital disorders were identified. The coverage has been greater than 98% and the repetition rate for insufficient samples less than 1.9%.

Mechanistic Bases of Neurotoxicity Provoked by Fatty Acids Accumulating in MCAD and LCHAD Deficiencies

Abstract Fatty acid oxidation defects (FAODs) are inherited metabolic disorders caused by deficiency of specific enzyme activities or transport proteins involved in the mitochondrial catabolism of fatty acids. Medium-chain fatty acyl-CoA dehydrogenase (MCAD) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiencies are relatively common FAOD biochemically characterized by tissue accumulation of medium-chain fatty acids and long-chain 3-hydroxy fatty acids and their carnitine derivatives, respectively. Patients with MCAD deficiency usually have episodic encephalopathic crises and liver biochemical alterations especially during crises of metabolic decompensation, whereas patients with LCHAD deficiency present severe hepatopathy, cardiomyopathy, and acute and/or progressive encephalopathy. Although neurological symptoms are common features, the underlying mechanisms responsible for the brain damage in these disorders are still under debate. In this context, energy deficiency due to defective fatty acid catabolism and hypoglycemia/hypoketonemia has been postulated to contribute to the pathophysiology of MCAD and LCHAD deficiencies. However, since energetic substrate supplementation is not able to reverse or prevent symptomatology in some patients, it is presumed that other pathogenetic mechanisms are implicated. Since worsening of clinical symptoms during crises is accompanied by significant increases in the concentrations of the accumulating fatty acids, it is conceivable that these compounds may be potentially neurotoxic. We will briefly summarize the current knowledge obtained from patients with these disorders, as well as from animal studies demonstrating deleterious effects of the major fatty acids accumulating in MCAD and LCHAD deficiencies, indicating that disruption of mitochondrial energy, redox, and calcium homeostasis is involved in the pathophysiology of the cerebral damage in these diseases. It is presumed that these findings based on the mechanistic toxic effects of fatty acids may offer new therapeutic perspectives for patients affected by these disorders.

Avaliação do custo-efetividade da incorporação do Espectômetro de Massa em Tandem no Programa Nacional de Triagem Neonatal no Brasil para diagnóstico da Fenilcetonúria e MCAD / Cost-effectiveness of the introduction of Tandem Mass Spectrometer in the National Neonatal Screening Program for diagnosis of phenylketonuria and MCAD

A Espectrometria de Massa em Tandem (MS/MS) é mundialmente considerada padrão ouro para a Triagem Neonatal (TN) de Erros Inatos do Metabolismo (IEM). Além de apresentar melhor sensibilidade e especificidade possibilita rastrear uma vasta gama de IEM usando um único teste. Atualmente o Programa Nacional de Triagem Neonatal (PNTN) rastreia cinco doenças (Fenilcetonúria, Hipotiroidismo Congênito, Fibrose Cística, Hemoglobinopatias e Deficiência da Biotinidase). Uma das metas do PNTN é o aprimoramento e a incorporação de novas doenças e/ou tecnologias. Com a recente recomendação da CONITEC (Comissão Nacional de Incorporação de Tecnologias) para aquisição do MS/MS para diagnóstico de doenças raras, vislumbra-se o incremento desta tecnologia para ampliação de doenças triadas, melhora da qualidade do teste diagnóstico, corroborando para melhorar qualidade de vida das crianças acometidas pelos EIM. Este trabalho teve como objetivo realizar uma análise de custo efetividade, para incorporação da tecnologia de tandem MS/MS na triagem neonatal, sob a perspectiva do SUS. Desta maneira buscou-se comparar diferentes cenários da TN com a tecnologia atualmente utilizada (Fluorimetria) somente para Fenilcetonúria (PKU), e com MS/MS para rastreio da PKU e da Deficiência de Cadeia Média Acyl-Coenzima Desidrogenase (MCAD). Para tanto construiu-se um modelo matemático de decisão baseados em cadeias de Markov que simulou a TN da PKU e da MCAD, bem como a história natural da MCAD. Foi acompanhada uma coorte hipotética de cem mil recém-nascidos. O horizonte temporal adotado foi a expectativa de vida da população brasileira de 78 anos de acordo com IBGE. Utilizou-se uma taxa de desconto de 5% para os custos e consequências clínicas para ambos os cenários propostos. Quando incorporado o MS/MS para triagem da PKU os ganhos em saúde continuaram os mesmos, pois o desempenho do MS/MS e da Fluorimetria foram praticamente iguais (efetividade), porém o custo incremental foi quatro vezes maior para a mesma efetividade, o que torna o MS/MS somente para PKU não custo efetiva (dominada). No entanto, quando analisado o cenário do MS/MS para triagem da PKU e da MCAD o custo incremental do MS/MS no PNTN foi menor por causa da economia feita uma vez que é possível realizar ambos os testes no mesmo o teste do pezinho atual

Diagnostico de la deficiencia de Acil-CoA deshidrogenasa de cadena media mediante el uso de sustratos tritiados / Diagnosis of medium chain ACYL Co-A dehydrogenase deficiency using tritiated substrates

La acil-CoA deshidrogenasa de cadena media (MCAD) cataliza la primera reacción de la degradación de ácidos grasos de 10 a 12 átomos de carbono. Su deficiencia debe ser siempre confirmada por estudios de laboratorio. En el presente trabajo, fueron incubados fibroblastos de pacientes que presentaban la deficiencia de MCAD, en presencia de sustratos tritiados. Fue encontrada diferencia significativa (P<0,05) al comparar la degradación de palmitato y miristato tritiado entre controles y pacientes con deficiencia de MCAD. Se observo más deprimida la oxidación de miristato tritiado que la de palmitato tritiado.

The medium-chain acyl-CoA dehydrogenase (MCAD) is the key enzyme for degrading fatty acids with a chain of 10 to 12 atoms of carbon. Its deficiency should be confirmed using laboratory methods. During the present work, fibroblasts from patients who presented MCAD deficiency were incubated, in tritiated substrates. A significant difference (P<0.05) was found when comparing palmitate and miristate between controls and patients with MCAD deficiency. The triatiated miristate presented a more depressed oxidation in comparison to palmitate.

A Suspect Case of Medium Chanin Acyl-Coenzyme A Dehydrogenase Deficiency with Iron Deficiency Anemia / 대한소아혈액종양학회지

Iron deficiency anemia is a common disorder during infancy and childhood. Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common disorder of mitochondrial fatty acid oxidation. However, this metabolic disorder is extremely rare among Asians. Generally MCAD deficiency patients are healthy until initial presentation of hypoketogenic hypoglycemia and encephalopathy which is predisposed by an intercurrent illness and/or a period of poor oral intake. The first attack causes a high risk of mortality or permanent neurologic sequelae. The authors report a suspect case of MCAD deficiency with iron deficiency anemia, with a brief review of related literatures.

The Prevalence of A985G Mutation in Medium Chain Acyl-Coenzyme A Dehydrogenase (MCAD) Gene in Neonates Determined from Guthrie Card

PURPOSE: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disoder of beta oxidation of fatty acids and characterized by episodic hypoglycemia, vomiting, convulsion, encephalopathy, apnea, and sudden death related to fasting or infection resembling Reye syndrome or sudden infant death syndrome. In acute stage, mortality rate is very high and survivors have significant risk of developmental disability and chronic somatic illness. However, the high mortality and morbidity can be totally prevented by appropriate dietary management on the basis of early and accurate diagnosis. Recently, a single point mutation (A985G) in the MCAD gene has been described that accounts for most of MCAD deficiency. The prevalence of MCAD deficiency shows marked racial differences. And population-based DNA screening for this potentially fatal disorder might be justified in countries with high frequency of the mutation. The prevalence of A985G mutation in the MCAD gene was studied in neonates using Guthrie cards for neonatal screening. METHODS: Dried blood spots on Guthrie cards originally used for neonatal screening programs obtained from 500 live newborn babies born in a private obstetric clinic or Seoul Red Cross Hospital in Seoul during the period from Jan. 1, 1995 to Jul. 31, 1995 were collected. DNA was extracted from the dried blood spots, and a segment of the MCAD gene was amplified from the DNA using polymerase chain reaction technique. The PCR products were electrophoresed on a polyacrylamide gel after treatment of a restriction enzyme, NcoI. And the restriction pattern was analyzed with ethidium bromide staining of the gel. RESULTS: The PCR was successful with all DNAs from Guthrie cards. And the A to G transition at nucleotide position 985 in the MCAD gene was not demonstrated in any of the specimen. Conlusions : 1) The frequency of A985G mutation in the MCAD gene is extremely low in Korean population. 2) The methodology used in this study can be applied to population-based molecular genetic studies for other hereditary diseases.

The Prevalence of A985G Mutation in Medium Chain Acyl-Coenzyme A Dehydrogenase (MCAD) Gene in Neonates Determined from Guthrie Card

PURPOSE: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disoder of beta oxidation of fatty acids and characterized by episodic hypoglycemia, vomiting, convulsion, encephalopathy, apnea, and sudden death related to fasting or infection resembling Reye syndrome or sudden infant death syndrome. In acute stage, mortality rate is very high and survivors have significant risk of developmental disability and chronic somatic illness. However, the high mortality and morbidity can be totally prevented by appropriate dietary management on the basis of early and accurate diagnosis. Recently, a single point mutation (A985G) in the MCAD gene has been described that accounts for most of MCAD deficiency. The prevalence of MCAD deficiency shows marked racial differences. And population-based DNA screening for this potentially fatal disorder might be justified in countries with high frequency of the mutation. The prevalence of A985G mutation in the MCAD gene was studied in neonates using Guthrie cards for neonatal screening. METHODS: Dried blood spots on Guthrie cards originally used for neonatal screening programs obtained from 500 live newborn babies born in a private obstetric clinic or Seoul Red Cross Hospital in Seoul during the period from Jan. 1, 1995 to Jul. 31, 1995 were collected. DNA was extracted from the dried blood spots, and a segment of the MCAD gene was amplified from the DNA using polymerase chain reaction technique. The PCR products were electrophoresed on a polyacrylamide gel after treatment of a restriction enzyme, NcoI. And the restriction pattern was analyzed with ethidium bromide staining of the gel. RESULTS: The PCR was successful with all DNAs from Guthrie cards. And the A to G transition at nucleotide position 985 in the MCAD gene was not demonstrated in any of the specimen. Conlusions : 1) The frequency of A985G mutation in the MCAD gene is extremely low in Korean population. 2) The methodology used in this study can be applied to population-based molecular genetic studies for other hereditary diseases.