Use of the Investigator ESSplex SE QS Kit (QIAGEN) at Half PCR Reaction Volumes for the Analysis of Forensic Samples

The Investigator ESSplex SE QS Kit (Qiagen) is a next-generation polymerase chain reaction (PCR) kit that, in 60 min, amplifies 17 Short Tandem Repeat (STR) markers, including the five European Standard Set (ESS) loci (D10S1248, D12S391, D1S1656, D22S1045, D2S441), the SE33 marker, and the locus Amelogenin for sex determination. Two quality sensors (QS1 and QS2) are also co-amplified to check PCR performance. Since forensic laboratories carry out hundreds of DNA typings annually, we verified the kit’s performance using half reaction volumes with the aim of improving the number of samples that may be amplified with a single kit and consequently reducing laboratory costs. In the present study, intended as a technical note rather than internal validation, some control samples (oral swabs) with known DNA profiles and 40 real casework samples were analyzed. We observed that reducing the total reaction volume, while keeping all component ratios unaltered, yields DNA profiles comparable to those obtained using standard reaction volumes and with allele peaks higher than those with regular volumes. Using half volumes for PCR amplification enables the analysis of a larger number of samples compared to the standard protocol, thereby reducing laboratory costs without compromising the quality of the analysis.