Author ORCID Identifier
https://orcid.org/0009-0000-5899-3621
Defense Date
2023
Document Type
Directed Research Project
First Advisor
Tracey Dawson Green
Second Advisor
Sarah Seashols Williams
Abstract
Disaster Victim Identification (DVI) refers to the process of forensic identification of unknown individuals following a mass disaster or fatality incident.1 In events of mass disaster, human dental structures are often the only viable DNA source remaining, as soft tissues are more easily degraded, contaminated, or otherwise compromised. Due to the protective nature of dental enamel and dentin surrounding the inner pulpal tissue, a labor-intensive sample preparation performed by extensively trained personnel is necessary to expose the nuclear material preceding the traditional forensic DNA workflow.2,3 In high volume cases, such as those often submitted for DVI, the current forensic laboratory procedures for tooth sample DNA processing have shown to simply be inefficient. Thus, this study evaluates the ability of the Applied Biosystems RapidHITTM ID instrument to produce viable short tandem repeat (STR) profiles from tooth samples when coupled with a simplified sample preparation protocol.4 Although the RapidHITTM ID instrument has been validated for use with buccal swab (reference) samples, minimal research exists describing its ability to process dental or skeletal remains.
In this study, a fast, low-tech tooth cleaning/preparation protocol, incorporating a Dremel® rotary tool and household hammer for pulverization, was developed and tested on a sample set of ten deciduous teeth, which were subsequently processed on the RapidHITTM ID instrument. Additionally, a parallel sample set of ten deciduous teeth of the same type and age were processed using the same cleaning protocol paired with a coffee grinder for fine-powder pulverization prior to being processed using a traditional forensic DNA laboratory-based workflow. All samples were stored at -20°C for approximately 1 to 21 years prior to processing.
The average percent of expected STR alleles detected from tooth samples processed on the RapidHITTM ID was 99.0%, whereas those processed manually using traditional methods was 99.8%. Although the average STR allele peak height for the RapidHITTM ID sample set is significantly lower (2483 RFU versus 4005 RFU for the manual set), both produced peak heights that were well within the internally validated optimal peak height ranges and well above established analytical and stochastic thresholds. Additionally, the average intralocus heterozygote peak height ratio was 0.80 for samples analyzed using the RapidHITTM ID, as compared to 0.86 for those processed manually, demonstrating acceptable intralocus balance. Not surprisingly, the RapidHITTM ID sample profiles exhibited greater interlocus imbalance; thus, caution should be used for analysis of challenged casework-type samples if more than a single contributor is expected. Minimal artifacts were noted in profiles of tooth samples analyzed using the RapidHIT TM ID, regardless of how aged the sample was; however, 9 of 10 samples analyzed did require analyst review due to incomplete adenylation (-A peaks) and/or pull-up resulting in high baseline noise in the Y-indel target area for female samples.
These results suggest that, when coupled with a simple, quick sample preparation protocol, the RapidHITTM ID instrument can successfully produce complete STR profiles from aged tooth samples with minimal allelic drop-out and high profile quality. Future studies should explore the viability of this method using more challenged tooth samples of varying ages, tooth pathologies, and those that are exposed to harsher environmental conditions. Further simplification of the sample preparation process should also be explored in order to make this approach more amenable to on-scene application.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
12-11-2023