Indications for appropriate referral to clinical genetics services - carrier testing

What carrier testing is

Carrier testing determines whether an asymptomatic individual carries a single copy of a pathogenic variant for an autosomal recessive (or X-linked) condition - relevant to reproductive planning rather than to the individual's own health risk
Increasingly offered proactively (reproductive carrier screening) to couples planning pregnancy or already pregnant, in addition to targeted testing when a specific familial variant or high-risk ethnicity/family history is known

Targeted carrier testing - testing a specific known familial variant in a relative of an affected individual or known carrier
Population/expanded carrier screening - testing for a panel of conditions (commonly including cystic fibrosis, spinal muscular atrophy, and fragile X, among others in expanded panels) regardless of family history, typically offered in the reproductive planning/early pregnancy context

Referral/testing indications: known familial pathogenic variant in a recessive condition, high-carrier-frequency ethnicity for a specific condition, consanguineous relationship (increases the chance both partners carry the same rare recessive variant), or as part of routine reproductive carrier screening programs
Testing both reproductive partners (rather than just one) is necessary to properly assess couple-level risk for an autosomal recessive condition - a single partner's carrier result alone does not determine offspring risk without knowing the other partner's status

A positive result in one or both partners triggers genetic counselling regarding reproductive options (preimplantation genetic diagnosis, prenatal diagnosis, donor gametes, or informed acceptance of the risk) - carrier status itself does not affect the carrier's own health in a fully recessive condition

Cystic fibrosis, spinal muscular atrophy, fragile X syndrome, thalassaemia/haemoglobinopathy carrier screening (particularly relevant in specific high-prevalence populations), preimplantation and prenatal genetic diagnosis

Reproductive carrier screening has shifted from purely targeted (family history-driven) testing toward broader population-based offering, reflecting evidence that most carrier couples for many conditions have no prior family history to prompt testing under the older targeted-only model

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