Several DNA testing companies have volunteered their services to help reunite immigrant families separated at the southern U.S. border.

But scientists and ethicists warn broad-based genetic tests are “overkill” and do not make sense for making such matches. Instead, if the government really needs help accurately reuniting immigrant families, it should consider a more basic paternity or maternity test, several say. Regardless of the test used, issues of privacy and consent need to be taken into account, experts say.

Last week Pres. Donald Trump reversed a policy his administration put in place that separated more than 2,500 children from their parents as they crossed into the U.S. illegally. The administration said in a statement Saturday more than 500 have been returned to their families, and that it plans to reunite the rest.

Yet questions have been raised about whether the administration has kept track of the identity and location of all the children, including a number of babies and toddlers who are too young to identify their parents. Late last week Rep. Jackie Speier (D–Calif.) asked the popular DNA testing company 23andMe to play a role in reuniting parents and children, and the company’s CEO agreed.

Finding a Genetic Match

The process of finding a genetic match between parents and children is pretty straightforward, says Ali Torkamani, director of genomics at Scripps Translational Science Institute. Paternity/maternity tests look at spots in the genome with so-called short-tandem repeats. These are areas where sequences of nucleotides—the A, C, G and T letters that make up DNA—are repeated potentially tens of times, varying in length from family to family, Torkamani says. There’s a lot of variability among family groups but also a lot of consistency between parent and child, he notes. A relationship can be established by looking at only a few dozen genome locations.

Regular paternity/maternity tests have an accuracy rate above 99 percent, says Kenneth Ryan, manager of Immigration Parentage Testing, based in Boston, which routinely uses such familial testing for immigration cases. “It’s pretty definitive when it’s used, in terms of [U.S. Citizenship and Immigration Services] accepting its results,” Ryan says. The tests become less accurate, however, with familial relationships further than parent–child, he adds. The turnaround for such test results in immigration cases is about a week, Ryan says, at a cost of about $550 per test. But the federal government could probably work out a far lower price for a high volume of tests, he says.

The FBI’s Combined DNA Index System, or CODIS, also uses these short tandem repeats—20 of them, instead of the 24 used by one popular paternity/maternity test—notes Henry Greely, director of the Center for Law and the Biosciences at Stanford University. All felons and people convicted of crimes can be compelled to provide DNA samples for CODIS, Greely says, and he thinks the immigrants in custody, including children, could be required to participate as well.

In contrast to paternity/maternity tests, Torkamani notes, consumer genetic testing offered by companies like 23andMe and MyHeritage look at hundreds of thousands of parts of the genome, revealing information that could pose ethical challenges. He described such tests as “overkill” for this circumstance.

Such DNA tests read single nucleotide polymorphisms (SNPs), or tiny genetic variations on the 22 pairs of non–sex-linked chromosomes and take far longer than paternity/maternity tests. MyHeritage, for example, reads 700,000 SNPs on the genome, says company spokesperson Rafi Mendelsohn—compared with a few dozen in a paternity/maternity test—and typically takes about a month to return results. Mendelsohn admits such a scope might not be needed simply to match a parent and child, but says the MyHeritage approach could be particularly useful if no family member has come forward to claim a child. The company, which has offered to donate 5,000 free tests, has genetic information from 1.4 million people in its database, he says, including many from South and Central America.

23andMe, whose tests reveal health and familial relationship information, has promised to use its tests solely for the purpose of reuniting families. “We are well aware that genetic data contains highly personal information and we want to ensure that it is handled confidentially and with the consent of anyone tested,” the company said in an e-mailed statement, noting it will offer its tests via nonprofit legal aid services. “Providing our testing through legal services ensures attorneys of the families can protect their privacy by only using this data to assist in reunification efforts.”

The biotech company Thermo Fisher Scientific has also offered to donate $1-million worth of its rapid DNA fingerprinting paternity/maternity test, RapidHIT, which only takes about 90 minutes and does not generate additional genetic information beyond paternity or maternity.

Issues of Consent

At least one legal aid group intends to decline such offers of help with genetic testing. “We are fielding a huge number of these offers,” a spokesman for RAICES, a nonprofit that provides legal services for immigrant children, families and refugees in Texas, wrote via e-mail. “We are not, nor are we intending, to employ DNA testing en mass [sic] for many reasons.”

A spokesperson for Ancestry.com, which offers a genetic test for establishing family relationships, wrote in an e-mail Sunday that the firm has significant concerns about maintaining the immigrants’ privacy under the current circumstances. “Ancestry’s mission is to connect people, and consumer privacy is our number one concern,” according to the statement. “The application of DNA testing for this purpose raises serious privacy and consent considerations that must be considered holistically before we would consider participating.”

Susan M. Wolf, a professor of law, medicine and public policy at the University of Minnesota, says it would be extremely difficult to get valid consent for genetic testing under these circumstances. A basic tenet of “consent” is that the decision has to be freely made and not coerced—the person has an actual choice. But a parent faced with not getting their child back if they do not get a genetic test really has no option other than to get the test, Wolf says. “What you really want is alternatives. You want the federal government to step up to the plate and say, ‘Yes, we do have [another] way of finding your child,’” she says, adding it is unclear whether the Trump administration does have another way.

Children, who will have to assent to giving blood or saliva for genetic testing, need someone to explain what is happening to them and why their samples are required, Wolf adds—and older children should have the right to agree or reject testing. She says she is also concerned that using genetic tests suggests “family” is defined solely as a close biological relationship, when in reality many families are more complicated. “What about the loving long-time caregiver who may not be genetically related to that child?” she says. “Those families deserve reunification, too.”

If genetic testing is used at all, the government or other entities should not use or keep the immigrants’ data beyond what is needed for reunification, Wolf says. And testing would need to be part of a larger, organized and rapid reunification process. “Genetics may have a limited role to play,” she notes, “but it’s never going to be the be-all and end-all.”