NIST Interlaboratory Mixture Interpretation Study 2005 (MIX05)

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[Poster summarizing sample selection presented at Promega meeting Sept 2005]

The present interlaboratory challenge exercise will be one involving only data interpretation. Laboratory differences due to instrument sensitivities and PCR amplification variability will be removed from this comparison study. Mixtures representing four different case scenarios have been generated at NIST with multiple STR kits and provided to laboratories as electropherograms.

Enclosed you will find electronic data files (as Mac or NT files per your request) from four different mock sexual assault cases that are part of the latest NIST interlaboratory study known as MIX05. In each case, we are providing the “evidence” sample result, which is a mixture of at least one perpetrator and a victim. The “victim” reference sample is also being provided for each scenario. Included in this data package are results from five different STR kits: Profiler Plus, COfiler, SGM Plus, Identifiler, and PowerPlex 16. Results from all kits were obtained from the same lot of DNA mixtures.  All .fsa files have been tested and shown to work properly with the provided kit-specific Genotyper macros and GeneMapperID v3.1.

The MIX05 interlaboratory study is designed to evaluate (1) the current “lay of the land” regarding STR mixture interpretation across the forensic DNA typing community and (2) to aid development of training tools to enable mixture interpretation and reporting.

Prior to March 15, 2005 we would like to receive the following information:

1)      Report the results as though they were from a real case including whether a statistical value would be attached to the results. Please summarize the perpetrator(s) alleles in each “case” as they might be presented in court—along with an appropriate statistic (if warranted by your laboratory standard operating procedure) and the source of the allele frequencies used to make the calculation. Please indicate which kit(s) were used to solve each case.

2)      Estimate the ratio for samples present in the evidence mixture and how this estimate was determined.

3)      Provide a copy of your laboratory mixture interpretation guidelines and a brief explanation as to why conclusions were reached in each scenario

As with previous NIST interlaboratory studies, each participant will receive (after providing results) a certificate of study participation, a summary report of the findings, and early access to any training materials developed out of this study.  Participants will be provided a review copy of the final report prior to its submission to a peer-reviewed journal. Results of individual laboratory or analyst performance will be provided directly to the lab upon request and overall study metrics will be reported in an anonymous fashion for publication in a peer-reviewed journal.

Thank you for your participation. Please contact us if you have any questions.

Download MIX05 Data: (click on desired file, then save to your computer in desired directory)

Profiler Plus

COfiler

Identifiler

SGM Plus

PowerPlex 16

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