Implementation of molecular cytogenetics for the rapid diagnosis of trisomy 21 and the incidence of Down Syndrome in the municipality of Campos dos Goytacazes, Brazil, in the period 2006-2008

• Autor(a) principal: da Silva, Antônio Francisco Alves
• Data de Publicação: 2008
• Outros Autores: Machado, Filipe Brum, Campos Fernandes, Regina Célia de Souza, Medina-Acosta, Enrique
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Revista Científica da Faculdade de Medicina de Campos
• Texto Completo: https://www.fmc.br/ojs/index.php/RCFMC/article/view/136
• topic: trissomia 21; Síndrome de Down; aneuploidia; citogenética molecular; marcador genético; trisomy 21; Down syndrome; aneuploidy; molecular cytogenetic assay,; genetic marker

Introduction: Down syndrome is the most commonly identified genetic form of mental retardation and one of the main causes of specific birth defects and medical conditions associated at birth. Three genetic mechanisms cause Down syndrome: free trisomy 21 (92-95%), mosaicism (2-4%) and translocation (3-4%). The clinical suspicion may be confirmed by the band G karyotype exam, the classic cytogenetic test that is considered gold standard. In addition to the delay in obtaining the results (1-6 moths), karyotyping in children requires the sample collection of >5 mL of peripheral blood, which is undesirable in cases of neonatal emergency. The Northern Region of the State of Rio de Janeiro lacks services that execute this exam, which, in turns, is remitted to laboratories localized in the cities of Rio de Janeiro, Belo Horizonte and São Paulo. Objectives: To implement in the municipality of Campos dos Goytacazes a specialized service that disposes a rapid genetic testor trisomy 21. Patients/Methods: Children born in the municipality of Campos dos Goytacazes within the period of January 2006 to November 2008, referred for clinical suspicion of Down syndrome by clinicians to the Molecular Identification and Diagnostics Unit - NUDIM, headquartered in the School Hospital Álvaro Alvim. The genetic test consists of typing and dosing alleles for five to eight DNA polymorphic markers specific for the long arm of the chromosome 21 (21q region) by the method of multiplexed quantitative fluorescence polymerase chain reaction. Results: There were 41 patients referred with clinical suspicion of Down syndrome. Thirty four of the cases (82,9%) had diagnosis confirmed by the DNA test. The majority (54%) of the affected children born to women > 35 year of age, confirming that advance reproductive maternal age is a factor for non disjunction of trisomy 21. Considering the annual mean rate of 7874 life births, an incidence of one affected by trisomy 21 in 695 infants was estimated for the municipality. Conclusions: The DNA test for trisomy 21 allowed confirming or ruling out the clinical suspicion, with results obtained in up to 48 hours from biological sample collection (mean of 7 days for turning in the results), enabling its use as a precise, rapid diagnostic test and, therefore, of easy insertion by monitoring, diagnostic and referring services.