Validation Information for Public DNA Laboratories
On this page find:
Overview of Validation
Validation refers to the process of demonstrating that a laboratory procedure is robust, reliable, and reproducible in the hands of the personnel performing the test in that laboratory. A robust method is one in which successful results are obtained a high percentage of the time and few, if any, samples need to be repeated. A reliable method refers to one in which the obtained results are accurate and correctly reflect the sample being tested. A reproducible method means that the same or very similar results are obtained each time a sample is tested. All three types of methods are important for techniques performed in forensic laboratories.
There are generally considered to be two stages to validation: developmental validation and internal validation. Developmental validation involves the testing of new STR loci or STR kits, new primer sets, and new technologies for detecting STR alleles. Internal validation, on the other hand, involves verifying that established procedures examined previously under the scrutiny of developmental validation (often by another laboratory) will work effectively in one's own laboratory. Developmental validation is typically performed by commercial STR kit manufacturers and large labs, such as the FBI Laboratory, while internal validation is the primary form of validation performed in smaller local and state forensic DNA laboratories.
Each forensic laboratory develops or adopts standard operating protocols (SOPs) that give a detailed listing of all the materials required to perform an assay as well as the exact steps required to successfully complete the experiment. In addition, SOPs list critical aspects of the assay that must be monitored carefully. SOPs are followed exactly when performing forensic DNA casework. [1]
Steps To Bring a Procedure On-line
The steps involved in bringing a procedure (assay, instrument, or software) on-line in a forensic lab typically include:
- Installation of the instrumentation or software and purchase of assay reagents
- Learning the technique and how to perform it properly
- Validation of the analytical procedure to define its range and reliability
- Creation of the standard operating procedures with interpretation guidelines based on the validation studies
- Training of other personnel on the technique
- Each trained analysts passing a qualification test for initial use in forensic casework
After a procedure has been successfully been implemented into use with forensic casework, proficiency tests are performed on a regular basis to demonstrate successful application of the technique over time by qualified analysts. [2]
Validation Summary Sheets
To aid current and future validation efforts by forensic DNA laboratories, the National Institute of Standards and Technology Biochemical Science Division has begun to catalog and summarize validation studies that have been published in the literature. The summaries will include details on the study conducted, a description of samples tested, and the number of samples run as part of the study.
These validation summary sheets will help the community meet SWGDAM Revised Validation Guideline 1.2.2: "internal validation studies must be sufficiently documented and summarized."
Validation Information to Aid Forensic DNA Laboratories on NIST's STRBase Website.
Note
[1] Butler, J.M. (2001) Forensic DNA Typing: Biology and Technology Behind STR Markers, San Diego: Elsevier Academic Press, Chapter 14 "Laboratory Validation", pp. 205-222
[2] Content on this page provided by the Biochemical Science Division,National Institute of Standards and Technology, STRBase Web site. Partial support for the design and maintenance of that website is provided by the Office of Justice Programs' National Institute of Justice through the NIST Office of Law Enforcement Standards.
