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Seattle Epidemiologic Research and Information Center (ERIC)


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Vietnam-Era Twin Registry Biospecimen Repository

The VET Registry has developed a system of protocols for the collection and storage of biological specimens that assures confidentiality for all participants. The biological specimens are stored at the Massachusetts Veterans Epidemiology Research and Information Center (MAVERIC) Core Laboratory is located at the VA Boston Health Care System in Boston, MA. The Laboratory staff has absolutely no phenotypic (non-genetic) information about VET Registry members, as the lab is completely blinded to the identity, disease characteristics, and any other research data collected from VET Registry members.

Before a VET Registry member decides whether to participate in the Biospecimen Repository, the procedures, confidentiality safeguards, and potential risks are explained in great detail. To be able to accommodate the wishes of members, a layered consent process is used which allows members to choose from several options with regard to how their biological specimen will be used in current or future research studies.

Members are informed that any future use of their samples will be approved by the VET Registry, in addition to an independent ethics committee that protects the rights and welfare of research subjects, this board is more commonly known as an Institutional Review Board or IRB. The Vietnam-Era Twin (VET) Registry maintains a repository of biological specimens obtained from Registry members. The VET Registry Biospecimen Repository includes DNA, plasma, and serum samples obtained from selected VET Registry members. As the VET Registry is a national resource for studies investigating genetic and non-genetic influences on health and disease in middle age men, this enhances the value of the information collected from VET Registry members to the research community.

Zygosity Testing for Research

DNA from the biorepository can be used to determine if twins are monozygotic (identical) or dizygotic (fraternal). By comparing the DNA of the 2 brothers, we can learn about the extent of relatedness in the 2 DNA samples. The DNA information can then be used to estimate—very accurately—if the twins share complete DNA information (both brothers originating from a single egg fertilized by a single sperm; i.e., monozygotic) or if they share partial information (each brother originating from 2 different eggs fertilized by different sperms; i.e., dizygotic). The VET Registry conducts DNA-based zygosity if there is DNA is available in the biorepository from both brothers of a twin pair as well as funding to pay for testing. Otherwise, the Registry relies on zygosity estimates based on standard questions twins have answered in past surveys. Zygosity estimates from these types of questionnaires are thought to be accurate 91% to 98% of the time (Forsberg, Goldberg, Sporleder, & Smith, 2010, PMID: 20874468, DOI: 10.1375/twin.13.5.461).