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Run-Specific Limits of Detection and Quantitation for STR-Based DNA Testing

NCJ Number
217224
Journal
Journal of Forensic Sciences Volume: 52 Issue: 1 Dated: January 2007 Pages: 97-101
Author(s)
Jason R. Gilder M.S.; Travis E. Doom Ph.D.; Keith Inman MCrim; Dan E. Krane Ph.D.
Date Published
January 2007
Length
5 pages
Annotation
This study used software (BatchExtract) from the National Center for Biotechnology Information as an alternative means of establishing limits of detection and quantitation for STR (short tandem repeat)-based DNA profiling that is more consistent with the methods used in other analytical disciplines that must account for background noise mixed with low levels of signal.
Abstract
The study found that the software could be used to determine objective run-specific thresholds for use in forensic DNA casework. The software was used to determine the height of each data-collection point for each dye along a control sample's electropherogram trace. These values were then used to determine a limit of detection (the average amount of background noise plus 3 standard deviations) and a limit of quantitation (the average amount of background noise plus 10 standard deviations) for each control sample. The application of the software was validated in analyses of the electropherogram data associated with the positive, negative, and reagent blank controls included in 50 different capillary electrophoresis runs. Currently, minimum thresholds established during laboratory validation studies have become the de facto standard for distinguishing between reliable signal and noise/technical artifacts in STR-based DNA profiling. These minimum peak height thresholds generally fail to consider variability in the sensitivity of instruments, reagents, and the skill of human analysts involved in the DNA profiling process over time. The alternative method described in this paper addresses these limitations. The paper's description of materials and methods used in the study focuses on baseline noise determination and the test mixture. 2 tables, 2 figures, and 18 references