Validation of new features in Applied Biosystems^TM 3500 Series Data Collection Software version 4 for forensic STR typing

Abstract

 New features for forensic STR typing have become available on 3500 Series Data Collection Software version 4 (DC v4). To investigate impacts of the new features on the interpretation of electropherograms is important to maintain and improve the objectivity and reliability of forensic STR typing. In this study, we assessed and investigated fundamental performance, signal optimization, and pull-up reduction with enabling and disabling the new data optimization features. In fundamental performance verification, although the data generated with the run module-dependent signal optimization showed a tendency to decrease the peak height slightly, all the data set generated from a different combination of enabled and disabled features tested in this study were comparable. In electropherograms generated with the run module-dependent signal optimization, some artifact peaks were observed at lower molecular weight region from the presumed parent allele peaks in the same dye-channel. The number of pull-up peak observations in electropherograms generated with the pull-up reduction feature was decreased compared to when the feature was disabled. However, distributions of distances of a pull-up peak from the corresponding parent peak and morphologies of pull-up peaks were different between the dataset obtained from the pull-up reduction feature enabled and that obtained from the feature disabled in certain pull-up patterns. Therefore, forensic biologists must be aware of those differences when interpreting electropherograms. We conclude that it is useful to use DC v4 with the run module-dependent signal optimization feature disabled and the pull-up reduction feature to obtain electropherograms with less artifact peaks.