Comparison of six commercially available STR kits for their application to touch DNA using direct PCR

Belinda Martin, Duncan Taylor, Adrian Linacre

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Abstract

With an increase in the application of direct PCR to items of forensic relevance, as well as the array of STR kits available for amplification, the need for a comprehensive investigation into the optimum STR panel for this workflow has arisen. Here we examine the relative STR amplification success of touch DNA on a range of substrates, with surface properties typical of those found in forensic investigation, using six commercially available STR kits: GlobalFiler®, Identifiler® Plus, Identifiler® Direct, VeriFiler™ Plus, Investigator® 24Plex QS, and PowerPlex® 21. We report on the percentage of possible donor alleles amplified per profile, and the number of samples that resulted in informative genetic data (≥12 autosomal alleles). We also include comment on the ease of interpretation of the resulting electropherograms for each of these six STR kits, when applied within a direct PCR workflow. Donors of known shedder status deposited DNA by handling one of five substrates (glass slide, matchstick, insulated wire, circuit board, and a plastic ziplock bag) for 15 s, 15 min post-handwashing with water. Each item was touched in triplicate by each volunteer for amplification with each STR kit resulting in a dataset of 720 samples. The difference in the number of profiles considered to be informative was found to be statistically significant when comparing STR kits (p = 0.0011) and donors (p = 2e-07), but not when considering substrates (p = 0.15). Identifiler® Plus amplification resulted in the highest profile coverage and second highest percentage of informative profiles. VeriFiler™ Plus generated informative profiles in the largest number of samples (94%) with PowerPlex® 21 amplification resulting in the fewest (79%). There was no significant difference between Investigator® 24Plex QS and GlobalFiler® in any empirical consideration; however, baseline noise and artefact presence made Investigator 24PlexQS profiles more difficult to analyse.

Original languageEnglish
Article number100243
Number of pages8
JournalForensic Science International: Reports
Volume4
DOIs
Publication statusPublished - Nov 2021

Keywords

  • Direct PCR
  • Human Identification
  • STR DNA Profiling
  • Touch DNA

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