Predicting the optimal STR profile amplification set up from Quantifiler™ Trio data

Abstract

Samples collected for forensic case work may be of varying quality and quantity. The sample DNA is often quantified prior to short tandem repeats (STR) profile analysis with methods such as Quantifiler™Trio (QFT). The QFT measures the quantity of DNA as well as an internal PCR control (IPC) and a degradation index (DI). The aim of this study was to use IPC and DI measurements to identify samples, which would benefit from a modified PCR amplification set-up when generating the STR profiles. The sample quality of 6287 single source case work samples were categorized as 'Good', ‘Partly degraded', ‘Highly degraded', ‘Inhibited' and ‘Degraded and Inhibited' based on the peak height ratios in the electropherogram data. The DI and IPC were correlated with the assigned quality categories of the samples. Samples categorized into the degraded and/or inhibited categories were found to have statistically significantly different DI and IPC compared to samples categorized as ‘Good'. This indicates that the additional information gained from the QFT can be useful to identify degraded and/or inhibited samples prior to the STR-profile analysis. Future work will re-evaluate the criteria of inclusion in the sample quality groups and implement multi source samples.