Evaluating the efficiency of DNA extraction methods from different substrates

Abstract

The efficiency of extracting DNA directly from substrates varies according to a range of factors including the type of substrate and the extraction technique. Two routinely used DNA extraction methodologies (automated DNA IQ and manual Chelex) were texts on their efficiency to extract DNA from a range of blood volumes (0.1–30 μL) on plastic and cotton. The efficiency of extracting DNA from plastic appeared to be lower than from cotton for both methods, but was only statistically significant for Chelex extractions. Pairwise comparisons of blood volumes extracted using DNA IQ showed statistically significant differences. Comparisons of Chelex extractions of different blood volumes also showed significant differences for cotton, but not for plastic. The threshold effect of DNA IQ was only demonstrated at blood volumes above 15 μL. This preliminary research highlights discrepancies between extraction methods and demonstrates that laboratories should be aware of the limitations of their analysis techniques, as knowledge of extraction efficiencies may assist in optimisation of methodologies and procedures. Extraction efficiency analysis will also allow for more accurate assessment of the influence of used methodologies in studies relating to determination of DNA transfer rates, and, should these transfer studies be put into practice, in casework.