The Scientific Working Group on DNA Analysis Methods (SWGDAM) has released interpretation guidelines for forensic DNA testing laboratories performing next generation sequencing (NGS). Two documents have been published on the SWGDAM website:
Addendum to “SWGDAM Interpretation Guidelines for Autosomal STR Typing by Forensic DNA Testing Laboratories” to Address Next Generation Sequencing [view here]
Interpretation Guidelines for Mitochondrial DNA Analysis by Forensic DNA Testing Laboratories (revised) [view here]
Publication of these guidelines is a major step that assists operational forensic laboratories in implementing NGS and increasing positive casework impacts. It meets a request from the U.S. National DNA Index System (NDIS) Procedures Board for interpretation guidelines to facilitate NGS-based NDIS submissions. Therefore, this also enables near-term NDIS approval of the MiSeq FGx® Forensic Genomics System. ***Update 5/2/2019: NDIS approval has now been granted. Read more here.***
The addendum to the autosomal STR typing guidelines highlights the similarities between CE- and NGS-generated data interpretation and provides information and guidance on NGS-specific interpretation concepts regarding:
- Sequence-based allele designation
- Analytical and stochastic thresholds
- Application of sequence-based allele frequency data for statistical analysis
- Mixture interpretation, including examples demonstrating how isoalleles (alleles of the same length differentiated by sequence) may be used to:
- Improve number of contributor estimation
- Better deduce major and minor donor profiles utilizing sequence information to differentiate, or “unmask”, minor donor alleles that share the same length as major donor alleles or stutter positions
The mtDNA guidelines were revised from the previous 2013 version to incorporate NGS methods and, as stated in the guidelines introduction, to “more accurately reflect the current state of the field and to better serve forensic mtDNA practitioners.” Updated sections include sequence analysis criteria, mixture interpretation and interpretation of C-stretches.
To review these SWGDAM documents, click here.
Do you want to learn more about NGS utility and implementation? Contact us today.
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