Four years ago, the team that created STRmix™ – probabilistic genotyping software that helped to revolutionize forensic science by enabling analysts to resolve mixed DNA profiles previously thought to be too complex to interpret – introduced FaSTR™ DNA analysis software.

With the ability to rapidly analyze raw DNA data and assign and estimate of the number of contributors (NoC), FaSTR™ DNA allows forensic laboratories to deliver an end-to-end analysis, interpretation, and intelligence solution when used in combination with STRmix™ and another STRmix team software, DBLR™, which is an investigative application designed for kinship analysis and rapidly calculating millions of likelihood ratios (LR).

FaSTR™ DNA works by applying a set of fully configurable rules to streamline the analysis of Short Tandem Repeat (STR) DNA profiles. In some instances, DNA analysis is more complex, and automated heuristics (analysis rules) alone may not be able to resolve all profiles. Where the intervention of a DNA analyst is required, FaSTR™ DNA readily provides all details related to possible ambiguity of a peak (i.e. stutter type, stutter ratio, composite stutter, pull-up potential, N/shoulder peak, peak morphology, stochastic homozygous threshold, heterozygote imbalance) and signals a requirement for the DNA analyst to intervene. All changes made by the analyst are highlighted and recorded.

The STRmix team has recently launched a new version of FaSTR™ DNA. Like its predecessor, FaSTR™ DNA v1.2, builds on existing capabilities and adds several major new features.

To see a brief overview of FaSTR™ DNA v1.2, visit https://vimeo.com/1007497807/85d479cea3?share=copy.

Driven by extensive engagement with the end-user community, the new version introduces several significant improvements to the analysis functionality, including the ability to detect known artifacts, an improved interface for pull-up investigation, options to view the electropherogram with either scan points or base pairs on the x-axis, and individual dye channel zoom capability. FaSTR™ DNA v1.2 also has the ability to model stutters by LUS or allele average using a stutter exception file to further align with the stutter files used within STRmix™. The project sample list is now organized into two tiers which allows viewing by sample type and/or sample status. In all analysis interfaces, a new search bar has been added which provides the ability to find samples by file name.

The most impactful improvement, though, is the addition of a new Review Module, which enables users to conduct the entire technical review workflow (with the epg profile and peak details in simultaneous view) to compare projects and complete all necessary conflict resolution actions within the software. Conflicts detected are any differences in peak label, the nature of peak classification, peak removal, ILS alignment, ladder allocation, and the assigned number of contributors.

The Review Module workflow compares two projects that were saved using the same analysis run set up or two identical runs, to accommodate a range of analysis workflows. These may include either:

• a two-reader workflow
• a single reader workflow
• variations of integrating the artificial neural network as a reader.

The electropherogram from each project is displayed in the Review Module. Three panes of the same dye channel are visible to identify the conflict peaks, the peak calls in each of the projects for review comparison, and the final review decisions (see figure below).

In addition, a new conflicts tab in the peaks table displays similar information. For each conflict peak, the calls and comments made in each project are displayed. To resolve a conflict, the review analyst actions a peak call, which is taken as the review call and the final state of the peak.

Alternatively, the reviewer may enter comments against conflict peaks for a different analyst to implement the analysis action. The peak data from the final review project can be exported as normal. The reviewed project can also be exported directly to STRmix™ for interpretation.

The summary report generated for the review project contains a summary of all peak conflict and resolutions and identifies the review analyst. While this represents a simple use case of the review module, alternative workflow options can also be accommodated.

In addition to these improvements, FaSTR™ DNA v1.2 brings many other new features including:

• Addition of a live display of total allelic peak RFU at each locus;
• Ability to search by sample name within the analysis sample list;
• Linking of sample status to the status of the associated ladder;
• Retention of samples failed at ILS in a project and ability to view raw data in Analysis Review;
• Ability to add more than one sample with the same name;
• Ability to customize detailed labels;
• Addition of a quality check to confirm the presence of quality markers in all samples (in applicable kits);
• Ability to save and view the NoC decision tree path and covariate information when a decision tree is used;
• Ability to view a method from within the analysis screen;
• Ability to save projects with different identifiers;
• Control over printing height for sample reports;
• Redesigned analysis sample list to facilitate the more streamlined use of FaSTR™ DNA with sample type and status;
• Ability to exclude samples from sample-to-sample and sample-to-database comparison checks;
• Display of the last saved project (.fpj) filename in the Analysis Review window;
• Ability to add a header and footer watermark to PDF reports;
• Addition of run outputs with information about the estimation of the number of contributors using the decision tree;
• Addition of a new help menu to show shortcut information within the software;
• Option to print electropherograms in scan points;
• Addition of a User Comments column to Export and Reporting windows;
• Ability to print electropherogram reports using custom dye colors; and
• Improvements in the Analysis Summary report.

For more information on FaSTR™ DNA v1.2, visit https://www.strmix.com/fastr.