An Initial Comparison of Applied Biosystems Quantifiler Duo and Promega Plexor HY Real-time PCR DNA Quantification Systems

Abstract

Objective 1: Sensitive Study: This study was designed to determine the quantity of template DNA below which amplification is not expected to yield a DNA profile. Dilution series of male and female stock DNA ranging from 0.003 ng/μl will independently be run with both Quantifiler Duo and Plexor HY. These samples will be run in duplicate per plate, with duplicate plates being run. We want to determine if the published lowest detection thresholds (0.023 ng/μl for Duo; 0.0032 ng/μl for HY) are concordant with the data obtained. Objective 2: Mixture Study: The purpose of this study is to obtain quantification results for mixtures of male and female DNA, which should allow for calculations of autosomal:Y ratios that can be helpful in determining what type of genetic analysis to pursue (autosomal STR, Y-STR, or both). Mixtures of female and male DNA ranging from 1:1 to 1024:1 (female: male) will be run in duplicate per plate, with duplicate plates being run. We want to find out how minor of a contributor the male can be in an excess of female DNA and still be detected. This is especially important in sexual assault cases where the major contributor is usually female or when the offender is a vasectomized male. Objective 3: Concordance Study: The purpose of this study is to compare quantification results from Quantifiler Duo and Plexor HY with those from Quantifiler Human, specifically in cases when samples are degraded. The majority of these samples originate from unidentified human remains. Patterns of overestimation or underestimation of DNA concentration can help determine which system will be most beneficial in these cases. This is where the new amplicons size featured in Quantifiler Duo is important in comparing the values with previous results for Quantifiler Human. Sample choice will be at the discretion of the laboratory technical leader and Unidentified Human Remains section analysts. These samples will be the ones that are known to be degraded and have previously yielded overestimated results from the Quantifiler Human quantification system, resulting in poor STR data.