The above letter was sent to Wenk and Chiafari, who offered the following reply (original) (raw)

Transfusion, 2000

Abstract

Increasingly, parentage testing laboratories are called upon to provide documentation of genetic linkage between individuals applying for legal immigration to the United States. Many embassies require that the party who has already obtained legal immigrant status document that the person(s) he or she is trying to bring into the United States is a first-degree relative, for example, establishing that the parties are parent and child. As part of this process, several embassies have started to request not only parent-child calculations, but also statistical tests for other possible relatedness, such as uncle-child or possible sibling status. In that context, Wenk and Chiafari1 demonstrate both the ways in which these indices are used and the fact that paradoxical results are often observed. Specifically, with the use of three highly informative VNTR loci, 4 of 25 examples of proven full-sibling pairs yielded a ratio of greater than 2:1 against full-sibling status. Furthermore, 2 of 25 pairs proven beyond doubt to be half-siblings had ratios exceeding 5:1 in support of full-sibling status. Because of the stringent immigration requirements, we typically test at 5 to 7 pairs of VNTR loci, which yields greater power to distinguish possible relationships. Our concern is with the ways that these indices are used by various US embassies with regard to issues of immigration. Recently, we had a case in which a married couple had legally immigrated to the United States and were trying to bring in their son. We tested the man and the boy at five highly polymorphic VNTR alleles. They (father and son) shared both alleles at three systems, and so the full-sibling index exceeded the father-child index by over 40-fold. Because of this latter calculation, the embassy refused admission of the boy to the country, despite the observation that the man was almost 40 years older than the tested child and hence far more likely to be the boy’s father than a full sibling! We subsequently tested the woman’s blood; this showed that the boy’s results were consistent with the two adults’ being his parents. It is not uncommon for genetic heterogeneity to be less diverse within a small ethnic community than in the entire classification of the race, and this gives an overrated significance to the sharing of more than a single allele. When alleles are common within a tested population, the sharing of two alleles will be correspondingly more common. This occurs even more frequently when less polymorphic systems, such as serial tandem repeats (STRs), are used. For example, alleles are more broadly distributed among all Asians than within the Japanese population alone. Hence, finding parents that share both alleles with children is not a rare event in which certain alleles are common within the tested population. In short, while we appreciate the challenges faced by embassies to follow the rules limiting immigration sponsorship to direct family members, we urge greater dialog between testing centers and the individual embassies, to establish reasonable expectations for additional testing requirements when no exclusions are found. One year after the initial testing was performed, the child in the above example remains abroad and separated from his parents. As the current system stands, families that can ill afford it are required to pay for additional testing and legal and communications costs. Jed B. Gorlin, MD Herbert F. Polesky, MD Memorial Blood Centers of Minnesota 2304 Park Avenue Minneapolis, MN 55404-3789 e-mail: jed@mbcm.org

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