Characterization of the pull-up reduction feature on Data collection 4 in forensic STR typing

Abstract

 Pull-up reduction feature (PUR) has been available since the update of the Data Collection Software version to 4. There is concern that data obtained from utilizing PUR might have some impact on the review and interpretation in STR typing by forensic biologists, because PUR changes the height of peaks under specific conditions. In this study, we first investigated the amount of reduction in peak height by PUR, then impact of PUR on remarkable peaks (e.g., an artifact comprised of a stutter peak and pull-up) was investigated. Fundamentally, the amount of reduction in peak height between PUR disable and enable showed a positive correlation with the parent peak height except for fluorescent dye red to purple. It was also confirmed that PUR functioned against the stutter peak shared with pull-up and irregular shape peak due to detected on the edge of an allele peak. For the mixture sample, the PUR impacted the minor contributor's allele peak which up to approximately 23.1% of the parent peak. Our data showed that the characteristics of PUR in reviewing artifacts and interpreting the STR typing should be taken into consideration.