Sensitivity and baseline noise of three new generation forensic autosomal STR kits: PowerPlex® Fusion, VeriFilerTM Plus and Investigator® 24plex QS

Abstract

Forensic laboratories are able to detect and analyse DNA template of lesser concentration due to improvements in technology, DNA extraction methods and analysis software. Several new autosomal STR kits have been released in response to the increase in the number of core autosomal loci included in the Combined DNA Index System (CODIS). In this study, we compared three of these STR kits, including the newly released Applied Biosystems VeriFiler™ Plus kit, the Promega PowerPlex® Fusion and the QIAGEN Investigator® 24plex QS kits for parameters related to trace DNA analysis, i.e. baseline noise, sensitivity and the prevalence of artefacts. The Investigator®24plex kit produced minimal background noise in the baseline of negative control samples, however, in the presence of DNA, the VeriFiler™ Plus kit produced the least amount of baseline noise. At the lowest input of DNA tested (8 pg), the VeriFiler™ Plus kit amplified an average of 50% of the expected alleles, compared to 25% with PowerPlex® Fusion and 4% with Investigator® 24plex. Full profiles were obtained with 63 pg of DNA for VeriFiler™ Plus and PowerPlex® Fusion compared to 125 pg for Investigator® 24plex. At low levels of DNA input, the PowerPlex® Fusion kit had the lowest number of artefacts in relation to average peak heights, whilst VeriFiler™ Plus had lower artefact numbers for high input samples (i.e. > 375 pg). Overall, the VeriFiler™ Plus kit was found to be most suitable for low template DNA samples, with high sensitivity and low levels of baseline noise. These performance characteristics provide a higher degree of confidence for differentiating trace DNA alleles from noise related artefacts. Keywords: Short tandem repeats, DNA amplification, Low template DNA, VeriFiler™ Plus, PowerPlex Fusion, Investigator 24plex QS