 |
 |
|
|||||||||||||||||
|
Proficiency testing
Collaborative exercise on DNA polymorphisms in bloodstains and/or other biological fluids Since 1992 the Spanish and Portuguese Group International Society for Forensic Genetics (GEP-ISFG, nowadays GHEP-ISFG) has organized a collaborative exercise to investigate DNA polymorphisms, with the objective of improving the standardization of methods and encouraging a meeting point to discuss the analytical strategies and different methodologies used by different laboratories. The exercise is coordinated by Josefina Gómez Fernández from the Quality Assurance Service at the Madrid Department of the National Institute for Toxicology and Forensic Sciences. These proficiency exercises lead to working meetings, forums of debate between the participants at which the difficulties inherent to the analysis of DNA polymorphisms are discussed, together with the practical and legal necessities that the analyses be done with the required quality. Since 1995 the exercise has functioned as a true control of quality, in that those laboratories reporting erroneous results at any of the markers are obliged not to use them in forensic cases until finding the cause of the error and until participating correctly in a subsequent exercise. The exercise is held annually, and comprises receiving various bloodstains and/or other biological fluid, simulating real casework, which are analyzed by the participating laboratories. The exercise not only consists of the analytical component but also a section on statistical analysis and in the reporting of results, with the objective of aiding the laboratories, not merely in confirming the results but also revealing the discrepancies of some laboratories to others, thus enabling the unification and consolidation of techniques and criteria. Until now 16 exercises have been held and the number of participating laboratories has increased, beginning with 10 laboratories during the first exercise and having more than 113 during the last, corresponding to the year 2010. The participating laboratories are situated in different countries, principally Spain and Portugal, although centres from Latin American countries are included. Most of the participating laboratories are public although the number of private laboratories is increasing. The studies are carried out using different PCR systems including loci on the Y and X chromosomes and include mitochondrial DNA analyses. Since 1995 the exercise has a paternity study. Despite the increase in number of participating laboratories, the results obtained have been satisfactory. These results have been published recently and those interested can consult the bibliographic listing. Undoubtedly the large number of markers used by the laboratories makes the proficiency exercise difficult to execute, unless in the future some standardization is introduced and the number of loci used is restricted. The results obtained in the paternity investigation section have also been satisfactory in spite of the different databases and allelic frequencies used; this confirms the recent advances in the standardization of the statistical methods employed. The effort spent to develop this exercise has been compensated by the significant acceptance shown, together with the good results that have been obtained. This, together with other activities initiated by the Group, should greatly help expand and unify the quality of the analyses performed in the forensic genetics laboratories located in Spain, Portugal and Latin America. Any laboratory interested can participate in the exercise. Each laboratory is assigned a code to ensure anonymity in the results generated. The exercise is held annually, with the samples being sent on the date established at the Group meetings. In 2010 the exercise fee was 125 euros for the paternity investigation section, and 150 euros for both the paternity investigation and forensic sections.
References
Gómez J. Carracedo A for the Spanish and Portuguese Working Group of the ISFH. A review of the collaborative exercises of the Spanish and Portuguese ISFH Working Group. Advances in Forensic Haemogenetics 6: 695-698 (1996). Gusmao L. et al. Mutation rates at Y chromosome specific microsatellites. Hum Mutat 26(6): 520-528 (2005). García-Hirschfeld J. et al. 2004-2005 GEP proficiency testing programs: special emphasis on the interlaboratory analysis of mixed stains. Progress in Forensic Genetics 11: 855-857 (2006). Montesino M. et al. Analysis of mtDNA mixtures from different fluids: an interlaboratory study. Progress in Forensic Genetics 11: 130-132 (2006). Crespillo M. et al. Results of the 2003-2004 GEP-ISFG collaborative study on mitochondrial DNA: focus on the mtDNA profile of a mixed semen-saliva stain. Forensic Science International 160: 157-167 (2006). Montesino M. et al. Analysis of body fluid mixtures by mtDNA sequencing: An inter-laboratory study of the GEP-ISFG working group. Forensic Science International 168: 42-56 (2007). Prieto L. et al. 2006 GEP-ISFG collaborative exercise on mtDNA: reflections about interpretation, artefacts and DNA mixtures. Forensic Science International: Genetics 2: 126-133 (2008). García-Hirschfeld J. et al. GEP-ISFG proficiency testing programs: 2007 update. Forensic Science International: Genetics Supplement Series 1 674-676 (2008). Gusmao L. et al. Results of the GEP-ISFG collaborative study on an X-STR Decaplex. Forensic Science International: Genetics Supplement Series 1 677-679 (2008). Sánchez-Diz P. et al. Population and segregation data on 17 Y-STRs results of a GEP-ISFG collaborative study. International Journal of Legal Medicine 122: 529-533 (2008). Gusmao L. et al. A GEP-ISFG collaborative study on the optimization of a X-STR decaplex: data on 15 Iberian and Latin American populations. International Journal of Legal Medicine 123: 227-234 (2009).
|
