Forensic evaluation of the QIAshredder/QIAamp DNA extraction procedure

The potential to recover genetic profiles from evidence samples has substantially increased since robust and sensitive amplification kits are commercially available. Nevertheless, even the best amplification kits cannot succeed when the extracted DNA is of poor quality. In this study we compared the efficiency of silica (QIAamp DNA Mini Kit), Chelex and Phenol-Chloroform (PC) based protocols to recover DNA from different categories of samples (blood and saliva on cotton swabs, muscles, cigarette butts, saliva on foods and epidermal cells on clothes). The efficiency of the QIAamp system was improved when samples were treated with QIAshredder homogenizing columns. Overall, conventional Chelex or PC protocols allowed to recover conclusive SGM Plus profiles for 61% of the samples considered in this study. Contrastingly, 82% of them were successfully genotyped after being treated with a combination of QIAshredder and QIAamp systems. Our results further suggested that the QIAshredder/QIAamp protocol was particularly helpful to analyze evidence samples with few DNA and/or that were collected on substrates containing PCR inhibitors.