SlimDna – An in-house expert system for STR profiling

Abstract

At NFC the internally developed software for DNA analysis, SlimDna is used. It is complementary to the LIMS and keeps track of samples, sample batches, instrument files and generated data. The system communicates with the LIMS, instruments and other software. SlimDna includes four modules (Analysis, Control, Administration and Frequency calculation) and covers the entire analysis process from DNA extraction to reporting approved STR profiles to the LIMS. SlimDna is built with Microsoft Internet Information Services (IIS) as application server and the user interface consists of Windows clients. For data storage MySQL is used. The software has been implemented in different packages, STR typing being the latest. The system has streamlined the STR typing by providing, among other functions, automated evaluation of STR profiles, databases for observed variant alleles as well as tracking and logging of negative and positive controls. STR electropherograms from analysis of crime scene samples (around 30 000 per year) are evaluated by SlimDna according to set rules concerning for example stutter ratio, heterozygote balance and number of alleles per marker in order to define the profile as a single source genotype or a mixture. The SlimDna output is compared to a manual evaluation before the results are reported to the LIMS. This process saves nearly one minute hands-on time per sample compared to the previous Excel-based solution. For reference samples, SlimDna evaluates the majority (55%) of the samples without manual revision. SlimDna’s automated interpretation has proven to be very accurate and will soon replace more of the manual revisions. In the near future, we aim to develop SlimDna further, with for example a mixture module supporting the reporting officers in analysis.