Applied Biosystems, a subsidiary of Applera Corp, has developed the Quantifiler Duo DNA Quantification Kit so that DNA evidence can be improved and also samples that were previously too challenging for previous analysis can now yield useful information.

It has been determined that a high percentage of the DNA samples submitted to forensic laboratories relate to sexual assault cases and the samples provide are often complicated mixtures of male and female DNA. This means that in at least 15 to 20 per cent of these cases there is no useful information recoverable.

The new Quantifiler Duo kit can now provide more information from previously intractable samples with just a single quantification reaction. The results that can be obtained include quantitative and qualitative data on total human DNA, human male DNA, and estimation of the quantity of DNA in degraded samples and also provides the male to female DNA ratio (the system can even detect very low quantities of male DNA when it is mixed with high quantities of female DNA).

The kit is able to integrate DNA analysis and allow results to be presented side by side for analysis. This allows the laboratory to make a more informed assessment as to whether samples are suitable for more sophisticated testing such as a standard short tandem repeat (STR) kit or a male-specific STR (Y-STR) kit.

The Quantifiler Duo kit has already been used successfully in trials by the San Diego Police Department forensic laboratory.

Patrick O'Donnell, the supervising criminalist at the San Diego Police Department's forensic laboratory commented: "We have been successful using the Quantifiler Duo kit and obtaining more precise information from samples that contain mixed gender DNA... Having the information about the characteristics of a piece of DNA evidence at the beginning of the testing process can be very powerful for guiding the forensic workflow toward better results in less time."

The Quantifiler Duo kit uses the same chemistry that is used on the Applied Biosystems real-time PCR system for the amplification, detection and quantification of DNA in a sample to guide STR chemistry selection as the next step in the analysis. If the kit detects a low quantity of male DNA mixed with a high quantity of female DNA then a more sample specific analysis kit can be used such as the male-specific DNA kit, or a Y-STR kit.

If a sample is found to be of low concentration or compromised on first analysis by the Quantifiler Duo then the more specific mini-STR kit (AmpFlSTR® MiniFiler™ PCR Amplification Kit) can be used.

The new chemical reagent kit will aid the forensic analyst in handling difficult samples allowing more information to be collected and a better assessment to be made of what repeat analysis is required, said Applied Biosystems.