Validation and implementation of the Investigator^® 24plex QS kit for forensic casework

Abstract

© 2017 Elsevier B.V. Advanced commercial STR multiplex systems containing the expanded CODIS core loci have been developed to achieve robust results for a wide range of inhibited and degraded forensic samples. To address these requirements and challenges, the new Investigator® 24plex QS kit (QIAGEN) was evaluated in this study which coamplifies all 23 recommended markers using 6-dye technology and incorporates an innovative internal control, the Quality Sensor (QS). The Quality Sensor, containing resultant alleles “Q” and “S” which is unique and patent pending, allows differentiation between robust amplification, degradation, inhibition, lack of amplification of DNA and failed PCR amplification. The performance of the Investigator® 24plex QS kit was evaluated using various sample types, a total of 130 samples from 25 forensic caseworks commonly encountered in our forensic laboratory during law enforcement investigation (homicide, sexual assault, robberies, criminal possession of a firearm, possession of a controlled substance, and property crimes-burglaries). The data indicates that the Investigator® 24plex QS kit produces an excellent “First Pass Success Rate” (full profile obtained with one amplification and one CE injection) with conclusive and reliable profiles, even when amplifying degraded or inhibited samples. Based on the results of this study, Investigator® 24plex QS Kit is rapid, achieves optimal results with difficult casework evidence samples and increases the detection of a minor contributor in mixtures. As an additional benefit, it improves the laboratory workflow due to the additional information given by the “Quality Sensor” and assists forensic experts in the selection of the most appropriate rework strategy.