title: Analysis of uni and bi-parental markers in mixture samples: Lessons from the 22nd GHEP-ISFG Intercomparison Exercise.
abstract: Since 1992, the Spanish and Portuguese-Speaking Working Group of the ISFG (GHEP-ISFG) has been organizing annual Intercomparison Exercises (IEs) coordinated by the Quality Service at the National Institute of Toxicology and Forensic Sciences (INTCF) from Madrid, aiming to provide proficiency tests for forensic DNA laboratories. Each annual exercise comprises a Basic (recently accredited under ISO/IEC 17043: 2010) and an Advanced Level, both including a kinship and a forensic module. Here, we show the results for both autosomal and sex-chromosomal STRs, and for mitochondrial DNA (mtDNA) in two samples included in the forensic modules, namely a mixture 2:1 (v/v) saliva/blood (M4) and a mixture 4:1 (v/v) saliva/semen (M8) out of the five items provided in the 2014 GHEP-ISFG IE. Discrepancies, other than typos or nomenclature errors (over the total allele calls), represented 6.5% (M4) and 4.7% (M8) for autosomal STRs, 15.4% (M4) and 7.8% (M8) for X-STRs, and 1.2% (M4) and 0.0% (M8) for Y-STRs. Drop-out and drop-in alleles were the main cause of errors, with laboratories using different criteria regarding inclusion of minor peaks and stutter bands. Commonly used commercial kits yielded different results for a micro-variant detected at locus D12S391. In addition, the analysis of electropherograms revealed that the proportions of the contributors detected in the mixtures varied among the participants. In regards to mtDNA analysis, besides important discrepancies in reporting heteroplasmies, there was no agreement for the results of sample M4. Thus, while some laboratories documented a single control region haplotype, a few reported unexpected profiles (suggesting contamination problems). For M8, most laboratories detected only the haplotype corresponding to the saliva. Although the GHEP-ISFG has already a large experience in IEs, the present multi-centric study revealed challenges that still exist related to DNA mixtures interpretation. Overall, the results emphasize the need for further research and training actions in order to improve the analysis of mixtures among the forensic practitioners.
authors: PRICAI-Fundación Favaloro, Buenos Aires, Argentina. Electronic address: utoscanini@pricai.com.ar.
authors: U
authors: U
authors: Toscanini
authors: DNA Diagnostic Laboratory (LDD), State University of Rio de Janeiro (UERJ), Rio de Janeiro, Brazil; IPATIMUP (Institute of Pathology and Molecular Immunology from de University of Porto), Porto, Portugal; I3s (Instituto de Investigação e Inovação em Saúde, Universidade do Porto), Porto, Portugal.
authors: L
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authors: Gusmão
authors: Laboratorio de Genética Regional Bogotá del Instituto Nacional de Medicina Legal y Ciencias Forenses., Bogotá, Colombia.
authors: M C
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authors: Álava Narváez
authors: Lab. de Identificación Genética. Depto. de Medicina Legal, Toxicología y Antropología Física. Facultad de Medicina. Universidad de Granada, Granada, Spain.
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authors: Álvarez
authors: Institute of Public Sanity Section of Legal Medicine Catholic University of Sacred Heart, Rome, Rome, Italy.
authors: L
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authors: Baldassarri
authors: Studio Indagini Mediche E Forensi (SIMEF), Reggio Calabria, Italy.
authors: A
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authors: Barbaro
authors: PRICAI-Fundación Favaloro, Buenos Aires, Argentina.
authors: G
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authors: Berardi
authors: Laboratorio Genética Forense, Instituto de Medicina Legal de Las Palmas, ULPG., Las Palmas, Spain.
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authors: Betancor Hernández
authors: Laboratorio de Genética Regional Suroccidente del Instituto Nacional de Medicina Legal y Ciencias Forenses., Cali, Colombia.
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authors: Policia de la Generalitat - Mossos d'Esquadra, Divisió de Policia Científica, Unitat Central del Laboratori Biològic, Sabadell, Barcelona, Spain.
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authors: Carreras-Carbonell
authors: Genética Forense, Unidad Criminalistica Contra la Vulneración de Derechos Fundamentales, Ministerio Público, Venezuela.
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authors: Castro
authors: Laboratório de Polícia Científica da Polícia Judiciária, Lisbon, Portugal.
authors: S C
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authors: Costa
authors: Institute of Criminalistics Prague, Prague, Czech Republic.
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authors: Coufalova
authors: Lab. Biológico de la Dirección Nacional de Policía Científica, Montevideo, Uruguay.
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authors: Domínguez
authors: DNA Diagnostic Laboratory (LDD), State University of Rio de Janeiro (UERJ), Rio de Janeiro, Brazil.
authors: E
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authors: Fagundes de Carvalho
authors: Instituto de Pesquisa de DNA Forense, IPDNA, Polícia Civil do Distrito Federal, PCDF, Brasília, Brazil, and Secretaria Nacional de Segurança Pública do Ministério da Justiça, SENASP/MJ, Brasília, Brazil.
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authors: STG
authors: Ferreira
authors: Laboratorio de Análisis de ADN- Facultad de Ciencias Médicas- Universidad Nacional de Cuyo, Mendoza, Argentina.
authors: S
authors: S
authors: Furfuro
authors: Forensic Science Unit, Forensic Genetics Section, Basque Country Police-Ertzaintza, Erandio, Bizkaia, Spain.
authors: O
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authors: García
authors: IPATIMUP (Institute of Pathology and Molecular Immunology from de University of Porto), Porto, Portugal; I3s (Instituto de Investigação e Inovação em Saúde, Universidade do Porto), Porto, Portugal.
authors: A
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authors: Goios
authors: Registro Nacional de ADN, Chile, Santiago de Chile, Chile.
authors: R
authors: R
authors: González
authors: CGC Genetics, Madrid, Spain.
authors: A González
authors: AG
authors: de la Vega
authors: GENOMICA, S.A.U., Madrid, Spain.
authors: A
authors: A
authors: Gorostiza
authors: Instituto Nacional de Toxicología y Ciencias Forenses, Delegación en Canarias, Santa Cruz de Tenerife, Spain.
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authors: Hernández
authors: Laboratorio de Biología Forense. Dpto Patología y Cirugía. Universidad Miguel Hernández, Elche, Alicante, Spain.
authors: S
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authors: Jiménez Moreno
authors: Unidade de Xenética, Departamento de Anatomía Patolóxica e Ciencias Forenses, Instituto de Ciencias Forenses, Facultade de Medicina, Universidade de Santiago de Compostela, and GenPop Research Group, Instituto de Investigaciones Sanitarias (IDIS), Hospital Clínico Universitario de Santiago, Galicia, Spain.
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authors: MV
authors: Lareu
authors: Comisaría General de Policía Científica - Laboratorio de ADN, Madrid, Spain.
authors: A
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authors: León Almagro
authors: Laboratorio de Genética Forense, Poder Judicial de Mendoza, Mendoza, Argentina.
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authors: Marino
authors: Servicio de Genética Forense, Superior Tribunal de Justicia de Entre Ríos, Paraná, Argentina.
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authors: Laboratorio Regional de Genética Forense del NOA - Departamento Médico - Poder Judicial de Jujuy, Jujuy, Argentina.
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authors: Miozzo
authors: Instituto de Genética Forense. Poder Judicial de Córdoba, Córdoba, Argentina.
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authors: Modesti
authors: Universita' Politecnica Delle Marche, DSBSP, Section of Legal Medicine, Ancona, Italy.
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authors: Onofri
authors: Biko SA, Montevideo, Uruguay.
authors: S
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authors: Pagano
authors: Instituto Nacional de Toxicología y Ciencias Forenses, Departamento de Sevilla, Sevilla, Spain.
authors: B
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authors: Pardo Arias
authors: NASERTIC, Villava, Spain.
authors: S
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authors: Pedrosa
authors: Unidad de Analisis de ADN, Colegio Oficial de Farmaceuticos y Bioquímicos, Buenos Aires, Argentina.
authors: G A
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authors: Penacino
authors: Serviço de Genética e Biologia Forenses, Instituto Nacional de Medicina Legal e Ciências Forenses, I.P. - Delegação do Norte, Porto, Portugal.
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authors: Pontes
authors: Serviço de Genética e Biologia Forenses, Instituto Nacional de Medicina Legal e Ciências Forenses, I.P., Coimbra, Portugal.
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authors: Porto
authors: LabGenetics. Laboratorio de Genética Clínica S.L., Madrid, Spain.
authors: J
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authors: Puente-Prieto
authors: Dirección General de la Policía, Granada, Spain.
authors: R Ramírez
authors: RR
authors: Pérez
authors: Serviço de Genética e Biologia Forenses, Instituto Nacional de Medicina Legal e Ciências Forenses, I.P.-Delegação Sul, Lisbon, Portugal.
authors: T
authors: T
authors: Ribeiro
authors: Banco Nacional de Datos Genéticos, Buenos Aires, Argentina.
authors: B
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authors: Rodríguez Cardozo
authors: Laboratorio de Biología y Genética Regional Noroccidente del Instituto Nacional de Medicina Legal y Ciencias Forenses., Medellín, Colombia.
authors: Y M
authors: YM
authors: Rodríguez Lesmes
authors: Servicio de Huellas Digitales Genéticas-Fac. Farmacia y Bioquímica-Universidad de Buenos Aires, Buenos Aires, Argentina.
authors: A
authors: A
authors: Sala
authors: Instituto Nacional de Toxicología y Ciencias Forenses, Departamento de Madrid. Servicio de Biología., Madrid, Spain.
authors: B
authors: B
authors: Santiago
authors: Unidad de Genética Forense, Servicio Médico Legal, Santiago, Chile.
authors: V G
authors: VG
authors: Saragoni
authors: Instituto Nacional de Toxicología y Ciencias Forenses, Departamento de Barcelona, Barcelona, Spain.
authors: A
authors: A
authors: Serrano
authors: IACA Laboratorios, Bahía Blanca, Argentina.
authors: E R
authors: ER
authors: Streitenberger
authors: Laboratorio Genia Geo, Montevideo, Uruguay.
authors: M A
authors: MA
authors: Torres Morales
authors: Laboratorio Regional Patagonia Norte de Genética Forense - Poder Judicial de Río Negro, Bariloche, Argentina.
authors: S A
authors: SA
authors: Vannelli Rey
authors: Instituto de Medicina Legal de Valencia, Valencia, Spain.
authors: M
authors: M
authors: Velázquez Miranda
authors: Genomic Engenharia Molecular, Sao Paulo, Brazil.
authors: M R
authors: MR
authors: Whittle
authors: Instituto Nacional de Toxicología y Ciencias Forenses, Departamento de Madrid. Servicio de Biología., Madrid, Spain.
authors: K
authors: K
authors: Fernández
authors: Unidade de Xenética, Departamento de Anatomía Patolóxica e Ciencias Forenses, Instituto de Ciencias Forenses, Facultade de Medicina, Universidade de Santiago de Compostela, and GenPop Research Group, Instituto de Investigaciones Sanitarias (IDIS), Hospital Clínico Universitario de Santiago, Galicia, Spain.
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authors: Salas
mesh_terms: D053523:Amelogenin / Q000235:genetics; D001774:Blood Chemical Analysis; D041321:Chromosomes, Human, X; D041322:Chromosomes, Human, Y; D016172:DNA Fingerprinting; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D053803:Forensic Genetics; D005819:Genetic Markers; D006239:Haplotypes; D006801:Humans; D007753:Laboratories / Q000592:standards*; D008297:Male; D018895:Microsatellite Repeats; D012463:Saliva / Q000737:chemistry; D012661:Semen / Q000737:chemistry
chemical_list: D053523:Amelogenin; D004272:DNA, Mitochondrial; D005819:Genetic Markers
keywords: Autosomal STRs; Forensic mixtures; GHEP-ISFG; Intercomparison Exercise; Y-chromosome; mtDNA