STR profiles from DNA samples with "undetected" or low quantifiler results

Area of Science:

• Forensic Science
• Molecular Biology
• Genetics

Background:

• Accurate DNA quantitation is crucial for successful short tandem repeat (STR) profiling in forensic analysis.
• Existing quantitation methods lack the sensitivity to reliably identify samples that will fail STR typing.
• Developing reliable screening methods is essential for optimizing forensic DNA analysis workflows.

Purpose of the Study:

• To evaluate the sensitivity of Quantifiler for identifying low-level DNA samples unlikely to yield STR profiles.
• To determine if a minimum Quantifiler quantitation threshold exists below which STR profiling consistently fails.

Main Methods:

• Low-level DNA samples from buccal swabs were extracted and serially diluted (0.002 to 0.250 ng/µL).
• DNA samples were quantified using Quantifiler.
• Quantified samples underwent Profiler Plus amplification and capillary electrophoresis for STR analysis.

Main Results:

• An absolute minimum Quantifiler value predicting complete STR typing failure could not be established.
• STR loci were successfully amplified and detected in 27% of samples Quantifiler initially "undetected".
• No STR alleles were detected in 73% of Quantifiler-"undetected" samples, indicating potential predictive value.

Conclusions:

• Quantifiler quantitation alone is insufficient to definitively predict STR profiling success or failure.
• Quantifiler data shows promise in identifying samples with a high probability of yielding no STR profile.
• Further refinement of screening methods is needed to improve the efficiency of forensic DNA analysis.