Technological advances will soon make rapid DNA testing (R-DNA) feasible and practical. But these new “lab on a chip” portable forensic DNA sampling systems also pose new challenges for the forensic DNA typing community. Validation guidelines for today’s lab-based DNA typing techniques exist and are employed throughout the forensic community. Analysts can run multiple tests on the same set of samples using a specific process and clearly see if results match. If the results don’t match, every step of the process is scrutinized to identify the cause. In a non-lab setting (e.g. booking station, battlefield), working with a “box” into which you insert and remove multiple chips during testing, traditional validation methods are not practical. Each chip contains all the necessary reagents for a DNA test and is disposed of after a single use. Because a chip is to be used only once, the challenge is to ensure that particular test, on that specific chip, is valid in generating the correct result.

Precedent Setting¹
For the past decade, processing each sample using current lab-based forensic DNA typing has taken about eight to ten hours. During this time period, the following steps are completed: DNA extraction, quantitation, polymerase chain reaction (PCR) amplification of multiple short tandem repeat (STR) loci, capillary electrophoresis separation with fluorescence detection and data analysis, and DNA profile interpretation. Each step in this workflow can take several hours to complete. For example, the PCR amplification portion of the workflow alone typically takes approximately three hours with standard thermal cycling protocols. The upcoming generation of rapid DNA instruments will dramatically reduce the time for DNA typing by using a rapid cycling protocol that includes considerably shorter PCR amplification times.

During DNA typing, PCR is used to create billions of exact copies of the human genomic DNA necessary for DNA typing. At the National Institute of Standards and Technology (NIST), we published a new PCR method in 2008 that reduces total thermal cycling time to approximately 36 minutes and includes the FBI’s 13 core loci. Our work enables a paradigm shift in forensic DNA analysis by successfully typing DNA in a shorter amount of time than with current methods. As a result, PCR is no longer a potential bottleneck in the quest for rapid DNA processing.

Limitations
Rapid DNA typing devices have a myriad of attractive applications, from screening at a point of interest to performing rapid STR analysis in the field. To be truly valuable, these devices must work reliably in less than two hours. Field applications will require portable and rugged devices. Results will be used for a specific purpose almost immediately so they must be robust and reliable. The device should require little user intervention and offer automated data interpretation.

The limitations imposed by requirements like reduced processing time and portability require us to question what degree of certainty is offered by current technologies. At NIST, we are collaborating with the FBI to test R-DNA platforms as a foundation for validation strategies. Rapid DNA technology could allow searching of DNA profiles collected at booking sites, similar to what is currently possible for fingerprints. However, expanding DNA typing and database access at police stations by non-lab personnel will require extensive evaluation, testing, and validation to ensure accurate DNA results.

To assist in this effort, a scientific working group for rapid DNA was established. This group was formed to monitor and address quality specifically in regard to the new generation of rapid DNA technologies and to help assess and validate these untested processes. The R-DNA working group will influence policy, define procedures, and discuss the potential implications of usage. Recommendations from this working group will guide the forensic DNA typing community in the proper use of the R-DNA devices.