Question

DAB Standard 6 contains requirements for the physical set-up of the laboratory facility.

Access to the laboratory is controlled and limited

Evidence examination, DNA extraction, and PCR set-up are conducted in separate places or at separate times.

Amplified DNA is confined to rooms separate from those used for other steps.

Robotic workstations used to carry out DNA extraction, quantification, PCR setup, and/or amplification in a single room must be in a separate room from initial evidence examinations.

Written procedures for cleaning and decontaminating facilities and equipment

Explain why each component of DAB Standard 6 is important. A sentence or two addressing each of the five standards under 6.1 is sufficient.

Answer 1

The DAB standards are standards set up by the DNA Advisory Board for quality assurance aand a quality program. The Board recommends that forensic labs obtain accreditation by adhering to these standards.

The five standards under DAB 6.1 are:

1) Access to the laboratory should be controlled and limited to prevent access to unauthorized persons.

Unauthorised individuals may tamper with the evidence and data. Data may be stolen and sold for financial gains. Information of murder suspects, if divulged may hinder investigations. Data such as address, contact numbers etc can be misused if leaked.

2. Examination of evidence, DNA extraction and PCR set up should be separated at different places or conducted at different times to prevent contamination.

Separation of the area into three parts, will prevent contamination of the sample DNA with PCR products. Contamination of the DNA sample will cause non-specific PCR products formed, which will affect analysis. In the initial investigation, right tissue or cells are selected for PCR. If amplified DNA from other investigation contaminates this sample, erroneous results will be obtained.

3. Amplified DNA should be placed in a different place than the place where DNA extraction, PCR etc is conducted.

Amplified DNA is more concentrated than pre-amplified DNA present in the sample. If the DNA sample to be amplified is contaminated with the amplified product, the amplified DNA will be preferentially amplified again, giving false positive results.

4. Robotic station for DNA extraction, PCR etc should be in a single room. No evidence examination should be done here.

Manual procedures can introduce contamination from the analyst skin during handling. Use of robotics will prevent manual contamination as well as reduce the time for the procedure. Further, these robotics will also prevent contamination from samples that are present in the initial examination room.

5. There should be procedures written for cleaning of the equipment and decontamination facilities.

Decontamination facilities are essential to remove any traces of patient sample before the PCR from another patient is used for amplification. PCR is a highly sensitive technique and even small amount of DNA present from the previous sample will cause erroneous result. Further, the samples may be from patients with infections. Decontamination of the equipments will prevent spread of infections.