ReviewCarrier testing in children and adolescents
Introduction
Genetic carrier testing for both autosomal recessive and X-linked conditions is performed primarily to provide information to individuals to enable future reproductive planning and informed choices. This is in contrast to testing to determine whether one is a ‘carrier’ of an autosomal dominant condition, where the purpose is to identify their risk of developing a genetic condition themselves. Results from this predictive or presymptomatic testing incur different psychological impacts that are beyond the scope of this review. There is a general acceptance that the best time to learn of one's carrier status is before, rather than during, pregnancy (British Medical Association Ethics Department, 2012). Although preconception carrier testing is strongly encouraged in adulthood, both with and without the presence of a family history of a genetic condition, population-based carrier screening is not widely available apart from in some specific communities, such as the Ashkenazi Jews, and certain regions, for instance Cyprus and Sardinia (Borry et al., 2011). Yet carrier testing in childhood is usually considered inappropriate (Borry et al., 2006). Although many international guidelines recommend testing should be postponed until age of majority, most commonly 18 years of age (Borry et al., 2006), consideration may be given to ‘mature minors’ who are less than 18 years but considered capable of making informed decisions about having genetic testing (Duncan and Delatycki, 2006).
Despite this, there are some circumstances in which carrier testing does occur in individuals who are less than 18 years of age. This testing might be intentional, in which carrier status is identified deliberately and is the goal of the test, or unintentional, where carrier status is identified as a by-product of testing that has been performed for other purposes. In this review we outline the situations in which carriers may be identified in childhood and the positions of professional guidelines that address carrier testing in children. We then review the arguments for and against carrier testing presented in the literature and compare this to the empirical evidence in this field.
Section snippets
Cascade carrier testing
There are two main situations when intentional carrier testing may occur. The first is in the context of a family history of a genetic condition, such as following the diagnosis of a child in the family. In this context, the parents and other adult family members are usually offered cascade testing to determine their carrier status. Although carrier testing is generally not recommended in any unaffected siblings of the affected child, technically this could also occur. The literature indicates
Unintentional or incidental carrier testing in children
Carrier status may be identified incidentally in three ways: through newborn screening, incidentally following diagnostic testing and during prenatal testing.
Guidelines and position statements
International guidelines typically do not support broad use of carrier testing or screening in children or adolescents, particularly for conditions where no medical benefit is derived from identifying carrier status (American Medical Association, 1995, ASHGBD, 1995, Committee on Bioethics et al., 2013, Human Genetic Society, 2008, Italian National Bioethics, 1999, Ross et al., 2013). A systematic review in 2006 identified 14 guidelines and position statements produced by 24 different groups
Ethical arguments for and against carrier testing in children
A number of arguments have been provided, both in professional guidelines and other opinion papers, against performing carrier testing in children. Often these arguments focus on the idea that performing carrier testing in childhood is not in the child's best interests.
Conclusions
Despite the cautious stance presented by the majority of the international guidelines that address carrier testing in children, a systematic review of the literature in 2010 identified that overall there is less evidence of psychosocial harm from carrier testing than predicted (Wade et al., 2010). However, the studies that have been conducted are small and limited in the contexts and variety of conditions for which testing has taken place. Further research is required, both for intentional and
Acknowledgements
Danya Vears would like to thank the Research Fund Flanders (Belgium), the Ministère de l’Économie, de l’Innovation et des Exportations du Québec, PSR-SIIRI-850 (Canada) and the Brocher Foundation, Geneva, Switzerland for their support.
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