Proficiency testing
Intercomparison program "Analysis of DNA polymorphisms in bloodstains and other biological samples"
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 19 exercises have been held and the number of participating laboratories has increased, beginning with 10 laboratories during the first exercise and having 123 participants during the last one, corresponding to 2011.
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 2012 the participation fee will be 125 euros for one of the Kinship and Forensic Modules, and 150 euros for both modules.
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).
Gómez J. et al. A review of the collaborative exercise on DNA typing of the Spanish and Portuguese ISFH working group. Int J Leg Med 110:273-277 (1997).
Gómez J. et al. The 1998-1999 collaborative exercises and proficiency testing program on DNA typing of the Spanish and Portuguese Working Group of the International Society for Forensic Genetics (GEP-ISFG). Forensic Sci Int 114(1): 21-30 (2000).
Alonso A. et al. Results of the 1999-2000 collaborative exercise and proficiency testing program on mitochondrial DNA of the GEP-ISFG: an interlaboratory study of the observed variability in the heteroplasmy level of hair from the same donor. Forensic Sci Int 125: 1-7 (2002).
Prieto L. et al. The 2000-2001 GEP-ISFG collaborative exercise on mtDNA: assessing the cause of unsuccessful mtDNA PCR amplification of hair shaft samples. Forensic Sci Int 134: 46-53 (2003).
Gusmao L. et al. Results of the GEP-ISFG collaborative study on the Y-chromosome STRs GATA A10, GATA C4, GATA H4, DYS437, DYS438, DYS439, DYS460, DYS461: population data. Forensic Sci Int 135: 150-157 (2003).
Sánchez-Diz P. et al. Results of the GEP-ISFG collaborative study on two Y-STRs tetraplexes: GEPY I (DYS461, GATA C4, DYS437 and DYS438) and GEPY II (DYS460, GATA A10, GATA H4, DYS439). Forensic Science International 135: 158-162 (2003). Forensic Sci Int 135: 158-162 (2003).
Gómez J. et al. The proficiency testing program on DNA typing of the Spanish and Portuguese Working Group of the International Society for Forensic Genetics (GEP-ISFG). En Progress in Forensic Genetics 9: 837-840 (2003).
Gómez J. et al. GEP proficiency testing programme in forensic genetics: Ten years of experience. Progress in Forensic Genetics 10: 124-126 (2004).
Salas A. et al. Mitochondrial DNA error prophylaxis: assessing the causes of errors in the GEP's 02-03 proficiency testing trial. Forensic Sci Int 148: 191-198 (2005).
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).