Pilot study for forensic evaluations of the Precision ID GlobalFiler™ NGS STR Panel v2 with the Ion S5™ system

With the continuous development of massively parallel sequencing (MPS), increasing numbers of laboratories have utilized this method for forensic genomic analyses. When sequencing common short tandem repeats (STRs), MPS does have many advantages over the length-based genotyping method that uses traditional capillary electrophoresis (CE) technology. The Precision ID GlobalFiler™ NGS STR Panel v2 was recently released to simultaneously target 31 autosomal STRs (20 expanded Combined DNA Index System (CODIS) core loci and 11 non-CODIS loci) and 4 gender determination loci (Amelogenin, DYS391, SRY and Y-indel (rs2032678)) with the Ion S5™ System. In the current study, we performed a preliminary validation for this novel MPS-STR panel that included the following analyses: repeatability, concordance, stutter and balance, sensitivity, case-type sample testing, stability, mixture and a population investigation. Complete and reliable profiles were obtained using 125 pg of positive control DNA. The commonly encountered types of case samples and artificial mixtures with ratios of 1:1, 1:3 and 3:1 were also fully genotyped. Additional allele sequence variations were detected in samples from 50 unrelated individuals, and subsequently, an increased power of discrimination and power of exclusion were achieved. However, the average depth of coverage (DoC) of the Penta D locus was detected to be dramatically lower than those of other loci, which caused an interlocus imbalance; this could be one of the reasons for the intralocus imbalance of this locus and the 0.18% inconsistent results in the concordance study. Although certain flaws were observed, the informative metrics, including the DoC, sequence coverage ratios (SCRs) and heterozygote balance (H_b), of the novel MPS multiplex in our study were sufficient for reliable sequencing results that were 99.61% in concordance with the capillary electrophoresis (CE) results. In general, the Precision ID GlobalFiler™ NGS STR Panel v2 was demonstrated to be sensitive, reliable and robust and could be a powerful tool for human identification and kinship analyses. Additionally, we look forward to its updated version.