noncarriers

Noncarriers are individuals who do not carry a pathogenic or likely pathogenic genetic variant in a gene or set of genes associated with a specified condition, as determined by molecular genetic testing or by known family genetic information. The term is most commonly used in the context of carrier screening and recessive diseases, where a noncarrier typically has two normal copies of the relevant gene, in contrast with a carrier who has one copy of the pathogenic variant.

In autosomal recessive conditions, noncarriers have zero copies of the disease-causing allele for the tested gene, whereas carriers carry one copy. For autosomal dominant or X‑linked conditions, testing results are usually described as pathogenic variant present or absent rather than as carrier or noncarrier, though the concept of being noncarrier can still apply to individuals without a familial pathogenic variant.

Testing methods used to identify noncarriers include targeted mutation testing, multi-gene panels, exome sequencing, and genome sequencing, along with pedigree analysis to interpret results. Results can be used in reproductive planning, including carrier screening for prospective parents, prenatal testing, preimplantation genetic testing, and donor screening for tissues or embryos.

Limitations exist: not all disease-causing variants are known or tested, and some tests may miss large deletions, duplications, or structural variants. Results may be affected by technical sensitivity, mosaicism, or variants of uncertain significance. Therefore, a noncarrier result does not guarantee absence of disease risk beyond the tested scope, and findings are usually discussed with a genetics professional for accurate interpretation and counseling.