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What should we be testing for in sperm and egg donors?

7 September 2020
By Sarah Norcross
Director, Progress Educational Trust
Appeared in BioNews 1062

Before someone can become a sperm donor or an egg donor in a clinical setting, they usually have to meet certain criteria, and undergo various tests and checks. This is to increase the chances of assisted conception being successful, and to reduce risks to the health of the resulting donor-conceived child.

In the UK and elsewhere, professional bodies have drawn up guidelines for screening donors, and these guidelines are revised periodically in line with the latest evidence and thinking. However, some clinics and services might also choose to employ additional tests.

One important way of assessing donors is carrier screening. Originally pioneered in the USA in 1971 (by Ashkenazi Jewish communities seeking to avoid the transmission of Tay-Sachs disease), and subsequently refined with advances in genetics, carrier screening involves finding out whether prospective parents – or prospective donors – carry gene variants that could lead to disease in a subsequent generation (even if the parent or donor is not affected by the relevant disease themselves).

Traditionally, carrier screening was performed for one gene at a time, and was offered for genes strongly associated with severe conditions (such as Tay-Sachs) that are either present from birth or manifest during childhood. However, in 2010 a so-called 'universal carrier test' became available for the first time, ushering in a new era of expanded carrier screening. This involves identifying simultaneously the presence or absence of many gene variants (potentially thousands), which might be associated with a vast number of different conditions (of varying severity and predictability).

Unlike traditional carrier screening, expanded carrier screening does not have to be guided or constrained by a person's individual or family history. For this reason, expanded carrier screening can sometimes lead to results that are unanticipated, or that are challenging to interpret.

However, a number of clinics and services in the private sector are now offering expanded carrier screening, as a way of assessing sperm and egg donors.

At this week's free-to-attend online event 'Careful What You Look For: What Should We Be Testing For in Sperm and Egg Donors?', produced in partnership with the Scottish Government, the Progress Educational Trust (PET) will be exploring questions including:

  • What conditions, or risk factors, is it practical and reasonable to screen for in sperm donors and egg donors? And what is it reasonable not to screen for?

  • Given that practically everyone is a carrier of at least some disease-related gene variants, does expanded carrier screening threaten to exclude most or all potential donors?

  • How can donors consent meaningfully to being screened for large numbers of conditions? And how can recipients of donor sperm or donor eggs make sense of such information about the donor?

  • What might the impact of expanded carrier screening be on the donor, and on the donor's own family (or plans for a future family)? Is there a role for genetic counselling?

Speakers at the event will include Professor Zosia Miedzybrodzka, Professor Scott Nelson, Dr Véronique Berman and Professor Guido Pennings.

SOURCES & REFERENCES
A universal carrier test for the long tail of Mendelian disease
Reproductive BioMedicine Online |  23 August 2010
Screening and prevention in Tay-Sachs disease: origins, update, and impact
Advances in Genetics |  2001
UK guidelines for the medical and laboratory procurement and use of sperm, oocyte and embryo donors
Human Fertility |  6 June 2019
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