Understanding Carrier Screening Results

Learn what positive, negative, and inconclusive carrier screening results mean and what to do next.

Most carrier screening results fall into one of three categories: negative, positive, or variant of uncertain significance. Understanding each type helps you know what follow-up steps may be needed.

A negative result means no disease-causing gene change was found for the conditions tested. This lowers risk but does not eliminate it entirely. No test detects every possible gene change, and some panels screen for more conditions than others.

A positive result means you carry a gene change for one of the tested conditions. For autosomal recessive conditions such as cystic fibrosis or SMA, the next step is usually to test your partner. If both partners carry a change in the same gene, there is a 25% chance with each pregnancy that the child will be affected.

A variant of uncertain significance means a gene change was found, but current science is unclear whether it causes disease. A genetic counselor can review whether updated testing or family studies are helpful.

For X-linked conditions such as fragile X syndrome, a female carrier has up to a 50% chance of passing the gene change to each child. Sons who inherit the change are more likely to be affected. A genetic counselor can explain reproductive risks and options.

References

• National Society of Genetic Counselors. Understanding Genetic Test Results. https://www.nsgc.org/
• ACOG. Carrier Screening FAQ.