An inter-laboratory study of DNA-based identity,parentage and species testing in animal forensic genetics

The probative value of animal forensic genetic evidence relies on laboratory accuracy and reliability.Inter-laboratory comparisons allow laboratories to evaluate their performance on specific tests and analyses and to continue to monitor their output.The International Society for Animal Genetics(ISAG)administered animal forensic comparison tests(AFCTs)in 2016 and 2018 to assess the limitations and capabilities of laboratories offering forensic identification,parentage and species determination services.The AFCTs revealed that analyses of low DNA template concentrations(≤300 pg/μL)constitute a significant challenge that has prevented many laboratories from reporting correct identification and parentage results.Moreover,a lack of familiarity with species testing protocols,interpretation guidelines and representative databases prevented over a quarter of the participating laboratories from submitting correct species determination results.Several laboratories showed improvement in their genotyping accuracy over time.However,the use of forensically validated standards,such as a standard forensic short tandem repeat(STR)kit,preferably with an allelic ladder,and stricter guidelines for STR typing,may have prevented some common issues from occurring,such as genotyping inaccuracies,missing data,elevated stutter products and loading errors.The AFCTs underscore the importance of conducting routine forensic comparison tests to allow laboratories to compare results from each other.Laboratories should keep improving their scientific and technical capabilities and continuously evaluate their personnel’s proficiency in critical techniques such as low copy number(LCN)analysis and species testing.Although this is the first time that the ISAG has conducted comparison tests for forensic testing,findings from these AFCTs may serve as the foundation for continuous improvements of the overall quality of animal forensic genetic testing.

Evaluation of the AGCU Expressmarker 16 and 22 PCR Amplification Kits Using Biological Samples Applied to FTA Micro Cards in Reduced Volume Direct PCR Amplification Reactions

This study evaluated the performance of the Wuxi AGCU ScienTech Incorporation(HuiShan,Wuxi,China)AGCU Expressmarker 16(EX 16)and 22(EX22)short tandem repeat(STR)amplification kits in reduced reaction volumes using direct polymerase chain reaction(PCR)amplification workflows.The commercially available PowerPlex21(PP21)System(Promega,Wisconsin,USA),which follows similar direct workflows,was used as a reference.Anticoagulate blood applied to chemically impregnated FTATM Micro Cards(GE Healthcare UK Limited,Amersham Place,Little Chalfont,Buckinghamshire,HP79NA,UK)was used to represent a complex biological sample.Allelic concordance,first‑pass success rate,average peak heights,heterozygous peak height ratios(HPHRs),and intracolor and intercolor peak height balance were determined.In reduced volume PCR reactions,the performances of both the EX16 and EX22 STR amplification kits were comparable to that of the PP21 System.The level of performance was maintained at PCR reaction volumes,which are 40%of that recommended.The EX22 and PP21 System kits possess comparable overlapping genome coverage.This study evaluated the performance of the AGCU EX16 and EX22 STR amplification kits in reduced PCR reaction volumes using direct workflows in combination with whole blood applied to FTATM Micro Cards.Allelic concordance,first‑pass success rate,average peak heights,HPHRs,and intracolor and intercolor peak height balance were determined.A concordance analysis was completed that compared the performance of the EX16 and EX22 kits using human blood applied to FTA Micro Cards in combination with full,half,and reduced PCR reaction volumes.The PP21 System(Promega)was used as a reference kit.Where appropriate,the distributions of data were assessed using the Shapiro‑Wilk test.For normally‑distributed data,statistics were calculated using analysis of variance(ANOVA)and for nonparametric data the Wilcoxon/Kruskal‑Wallis test was used.Statistical significance was set at P<0.05.Confidence intervals for mean values were set at 95%.On using reduced volume PCR reactions in combination with dried blood spots applied to FTA sample collection cards,both the EX16 and EX22 kits were shown to generate STR profiles of sufficient quality to allow entry into National DNA databases.The performance of both EX16 and EX22 was comparable to that of the PP21 System.This study demonstrates the successful use of the Wuxi AGCU ScienTech Incorporation EX16 and EX22 kits in reduced PCR reaction volumes with complex biological samples applied to chemically impregnated FTA sample collection cards.

Identification of Colored Dyes that are Resistant to Fading on Exposure to Ethylene Oxide;Use with Indicating FTA™Sample Collection Cards

Regulatory Standards and Forensic Communities are expressing an expectation for HID products to be certified as“DNA‑free.”Recently,“DNA‑free”status was described for HID‑related products using ethylene oxide(EtO);this gas reduces the presence of amplifiable DNA and causes minimal interference to downstream HID‑analytical methods.During sample collection,indicating cards,for example,Indicating FTA™(GE Healthcare Life Sciences,UK),are used to collect and store buccal cell DNA.These cards contain a dye which changes color on application of a colorless sample.Generating“DNA‑free”indicating cards using EtO should not impact the dyes’ability to indicate sample location or the efficacy of the card in downstream HID‑analytical methods.This study was initiated to identify alternative dyes to those currently used with sample indicating collection cards.The most promising,dyes when applied to cellulose papers exhibited a uniform color distribution and excellent sample indicating properties even when mixed with chemicals associated with FTA™.When dyed cellulose papers were exposed to EtO,ultraviolet radiation,elevated temperature,and humidity,negligible fading or discoloration was observed.The presence of these dyes on cellulose papers did not interfere with direct short tandem repeat(STR)profiling.Allelic concordance,first pass success rate,and mean peak heights were comparable to samples applied to Indicating FTA.Biological samples applied to EtO‑treated dyed cellulose papers and stored>1 month produced full STR profiles of sufficient quality to allow submission to DNA databases,confirming negligible interference from EtO treatment.These alternative sample indicating dyes resist EtO‑mediated fading while fulfilling the Forensic Community’s expectation for“DNA‑free”with negligible impact on collection card performance.