Two simplified tooth sample preparation methods for conventional laboratory and RapidHIT™ ID workflows

Disaster victim identification (DVI) refers to the forensic identification of unknown individuals following a mass disaster event. Human dental structures can contain viable DNA sources when other soft tissues are compromised. However, labor-intensive sample preparation performed by extensively trained personnel is needed to expose the nuclear material for traditional forensic DNA workflows. With this in mind, we evaluated two simplified sample preparation protocols for processing tooth samples using either a conventional forensic DNA workflow or the Applied Biosystems® RapidHIT™ ID instrument. Briefly, sample sets for both protocols included 10 deciduous teeth that were cleaned prior to either fragmentation with a claw hammer (for RapidHIT™ ID processing) or fine-powder pulverization with a consumer-grade coffee grinder (for traditional workflows). The average percentage of expected STR alleles that were detected above analytical threshold for these tooth samples were comparable between methods: RapidHIT™ ID = 99.0% and GlobalFiler™ = 99.8%. Average intralocus heterozygote peak height ratios (PHRs) were comparable: RapidHIT™ ID = 0.80 and GlobalFiler™ = 0.86. Importantly, 9 of 10 samples analyzed via the RapidHIT™ ID required analyst review for flagged artifact peaks and quality issues. Across all profiles, 91% of alleles passed quality metrics for the RapidHIT™ workflow versus 100% for conventional GlobalFiler™ analysis. Collectively, these results suggest that quick, low-tech tooth sample fragmentation followed by analysis with the RapidHIT™ ID instrument can produce complete STR profiles from aged tooth samples. Future studies should include larger samples sets, more challenging tooth samples, and further simplification of sample preparation to enable field-forward, on-scene DVI.