Multiplex assay for expanded core loci – have confidence in your evidence


With the increasing dependence on DNA profiling for human identification, in 2015, the FBI announced the completion of a validation project, adding seven new loci to the core CODIS set. These new STR markers improve the discriminatory power of DNA profiling kits and facilitate data sharing between international databases, which now have more loci in common. The Investigator 24plex QS Kit and Investigator 24plex GO! Kit meet the expanded CODIS set specifications, while also enabling a new level of workflow optimization.

Repeating STR analysis for failed samples can be costly and labor intensive and is often brought on by inhibition, degradation or absence of DNA. To help improve your forensic casework workflow, QIAGEN’s new Investigator STR QS Kits include a Quality Sensor (QS), which generates additional information about the sample quality. The QS is amplified alongside the STR markers and provides you with valuable information on the success of your amplification, as well as DNA degradation and/or inhibition.

By providing information on degradation and inhibition, the QS allows you to quickly determine if repeating steps will yield better outcomes and how to adjust your PCR setup to achieve optimal results. From a brief look at the electropherogram (EPG) you can confirm: 1. Successful amplification based on the presence of both the small amplicon Quality Sensor peak (QS1) and large amplicon Quality Sensor peak (QS2) that appear to be a similar height. 2. Absence of DNA by presence of both QS1 and QS2 at a similar height and no other sample peaks. 3. Failed PCR amplification by lack of both QS1 and QS1 and the absence of other peaks. 4. Inhibited DNA sample by normal QS1 peak height and reduced QS2 peak height. Sample peaks will generally decrease in height towards larger STR loci (ski-slope effect). 5. Degraded DNA sample when QS1 and QS2 appear at similar heights but sample peaks illustrate the ski-slope effect.

Sample Allele Peaks QS1 QS2 Interpretation
Present Present Present Successful amplification and profile
Absent Present Present No DNA
Absent Absent Absent Failed PCR
Ski-slope effect Present Reduced peak-height Inhibitors present
Ski-slope effect Present Present Degraded DNA

When processing evidence, you want to ensure you have an STR kit that you can trust. Check out the developmental validation paper demonstrating the robustness and reliability of QIAGEN’s Investigator 24plex QS and Investigator 24Plex GO! Kits and how it can improve your lab’s success and effectiveness.

Angela Cacioppo, MPS

Global Market Manager, Demand Generation

Angela joined QIAGEN in 2017. She received her Master's Degree in Forensic Science (biology track) from Pennsylvania State University. Before joining QIAGEN, Angela worked at The Bode Technology Group (a.k.a Bode Cellmark Forensics) as a DNA analyst, where she processed thousands of DNA samples and traveled the United States to testify as an expert witness. Afterwards, she joined LGC, where she was involved in the rollout and deployment of new and innovated technology, ParaDNA Systems, that facilitates the screening and triage of DNA samples.

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