Improving STR Profile Success Rates for Property Crime Specimens using InnoQuant® Human DNA Quantification & Degradation Assessment Kit

Abstract

Typical forensic casework DNA specimens may be degraded to varying degrees as a result of environmental insults, storage conditions, or age. These specimens may need to be excessively re-worked since their level of degradation may not be known until after amplification and typing. In this study, the InnoQuant ® Human DNA Quantification and Degradation Assessment Kit is used to provide an assessment of the level of degradation of property crime samples, demonstrating how it can be utilized to streamline a laboratory's workflow.215 actual casework property crime samples were first processed with Quantifiler ® Human and Identifiler ® Plus, and retrospectively quantified with the InnoQuant Kit. For samples that did not obtain any STR data, a quantification threshold was evaluated to determine how successfully each qPCR assay could be used as a screening test to identify samples with insufficient DNA for STR profiling. InnoQuant's long target exhibited the highest Area Under the receiver operating characteristic Curve (AUC=0.967), while exhibiting the highest true positive (sensitivity) and true negative (specificity) rates. For samples that did obtain some STR data, quantification values from each kit were compared with the number of STR loci successfully typed to see how well quantification data correlated with STR profiles. InnoQuant's long target (R 2 =0.80) correlated with profile success significantly better than the short target (R 2 =0.66) or the Quantifiler data (R 2 =0.61). Finally, samples that had sufficient DNA but did not yield full profiles were reamplified based on the InnoQuant data to determine if accounting for degradation can improve profile success. Additional alleles were obtained from all samples. The study demonstrates that InnoQuant can be a very effective tool in processing high throughput property crime specimens as a screening test to identify samples that will not produce DNA profiles and by providing more reliable quantification data to obtain optimal STR profiles.