The application of massively parallel sequencing to STR loci has initiated standardization processes necessary for forensic genetics. Specifically, rules to determine minimum reporting ranges for sequenced STR alleles and a nomenclature reflecting their variation were elaborated. The implementation of these ISFG recommendations [1], that include further prerequisites for kit-agnostic inter-laboratory exchange and comparability of the emerging data, is still pending. 

An essential element for any interpretation of the results of forensic STR analyses is a publicly available high-quality allele frequency population database. Here, the ISFG-endorsed STRidER (STRs for identity ENFSI reference) database and quality control platform [2] has been providing capillary electrophoresis (CE) frequency data since 2004, including its predecessor STRbASE, and has steadily expanded in loci, countries and services offered. The presentation of sequenced STR allele frequency datasets is impeded by the current heterogeneity of allelic sequence range output across kits and software used in the forensic genetic community, and the overall deviation from the recommended reporting ranges. For the allele sequences that expand beyond the “ISFG minimum range”, trimming solves the problem until harmonization in commercial kit output is reached‒but should not be performed manually on a population sample. The recent development of an automated trimming tool on STRNaming [3], the framework recommended for naming of sequenced STR alleles, constitutes an important step forward. The novel function enables easy and unambiguous adjustment of sequence batches to the ISFG minimum reporting range and has been tested on large datasets.

Now, the next step is determining the best format for offering sequenced STR allele frequency data on STRidER. Since sequencing adds the dimension of isometric alleles, a composite nomenclature and short identifier options beyond conventional CE, the presentation of information is more complex. Which details to include, and how to do that, are critical early decisions for the usability in downstream processes and software. STRidER has recently added a small STR sequence database in a preliminary format and invited for feedback with the aim of finding the data format that best serves the community from an initial stage. Results from the first months of this process of user involvement, the current status and the next steps forward will be presented.

Authors

• Martin Bodner (Institute of Legal Medicine, Medical University of Innsbruck, Austria)
• Jerry Hoogenboom (Netherlands Forensic Institute, Netherlands)
• Kristiaan J. van der Gaag (Netherlands Forensic Institute, Netherlands)
• Walther Parson (Institute of Legal Medicine, Medical University of Innsbruck, Austria)

References

[1] Gettings KB et al., FSI: Genetics 2024
[2] Bodner M et al., FSI: Genetics 2016, https://strider.online
[3] Hoogenboom J et al., FSI: Genetics 2021, https://www.fdstools.nl/strnaming/index.html