GHEP-ISFG collaborative exercise on mixture profiles (GHEP-MIX06). Reporting conclusions: Results and evaluation. (July 2018)

• Record Type: Journal Article
• Authors: Barrio, P.A.; Crespillo, M.; Luque, J.A.; Aler, M.; Baeza-Richer, C.; Baldassarri, L.; Carnevali, E.; Coufalova, P.; Flores, I.; García, O.; García, M.A.; González, R.; Hernández, A.; Inglés, V.; Luque, G.M.; Mosquera-Miguel, A.; Pedrosa, S.; Pontes, M.L.; Porto, M.J.; Posada, Y.; Ramella, M.I.; Ribeiro, T.; Riego, E.; Sala, A.; Saragoni, V.G.; Serrano, A.; Vannelli, S.
• Is Part Of: Forensic science international. Volume 35(2018)
• Page Start: 156
• Page End: 163
• Publication Date: 2018-07
• Subjects: DNA analysis -- Mixture interpretation -- Statistical evaluation -- Forensic genetics reporting -- Collaborative exercise -- Spanish and Portuguese-Speaking Working Group; Forensic genetics -- Periodicals; Génétique légale -- Périodiques; Forensic genetics; Electronic journals; Periodicals; 614.1
• DOI: 10.1016/j.fsigen.2018.05.005
• Languages: English
• ISSNs: 1872-4973

Abstract

Graphical abstract: Highlights: GHEP-MIX06 collaborative exercise makes an evaluation of mixture profiles reports. 25 forensic genetic laboratories from 8 different countries have participated. Reports issued, with a page number range of 1–11, do not completely fit to ISO/IEC 17025:2017 requirements. Most of laboratories use the same software ( LRmixStudio ), but with an important LR values dispersion. All laboratories that express LR in conclusions make a correct verbalization. Abstract: One of the main goals of the Spanish and Portuguese-Speaking Group of the International Society for Forensic Genetics (GHEP-ISFG) is to promote and contribute to the development and dissemination of scientific knowledge in the field of forensic genetics. Due to this fact, GHEP-ISFG holds different working commissions that are set up to develop activities in scientific aspects of general interest. One of them, the Mixture Commission of GHEP-ISFG, has organized annually, since 2009, a collaborative exercise on analysis and interpretation of autosomal short tandem repeat (STR) mixture profiles. Until now, six exercises have been organized. At the present edition (GHEP-MIX06), with 25 participant laboratories, the exercise main aim was to assess mixture profiles results by issuing a report, from the proposal of a complex mock case. One of the conclusions obtained from this exercise is the increasing tendency of participating laboratories to validate DNA mixture profiles analysis following international recommendations. However, the results have shown some differences among them regarding the edition and also the interpretation of mixture profiles. Besides, although the last revision of ISO/IEC 17025:2017 gives indications of how results should be reported, not all laboratories strictly follow their recommendations. Regarding the statistical aspect, all those laboratories that have performed statistical evaluation of the data have employed the likelihood ratio (LR) as a parameter to evaluate the statistical compatibility. However, LR values obtained show a wide range of variation. This fact could not be attributed to the software employed, since the vast majority of laboratories that performed LR calculation employed the same software ( LRmixStudio ). Thus, the final allelic composition of the edited mixture profile and the parameters employed in the software could explain this data dispersion. This highlights the need, for each laboratory, to define through internal validations its criteria for editing and interpreting mixtures, and to continuous train in software handling.