How can the results of this screening test be interpreted?
A negative result indicates that no significant mutations were detected in the genes tested. This significantly reduces the chances of the couple being carriers of the genes tested. A positive test indicates that a significant mutation was found, which means that the couple is carriers and are at an increased risk to have a child with a genetic disorder. If both the partners are carriers, there is a 25% chance of the baby being unaffected, 25% chance of the baby being affected and 50% chance of the baby being a phenotypically normal heterozygous carrier. In an autosomal recessive disorder, if only one partner is a carrier, there is 50% chance of the baby being unaffected and a 50% chance of the baby being a phenotypically normal heterozygous carrier. Early diagnosis and treatment help prevent life-threatening complications, where possible.
However, there is no test available that can detect all possible mutations that could cause a disorder, leaving behind a small chance (called a residual risk) of being a carrier even after a negative test result. Also, large heterozygous deletions cannot be detected by NGS accurately.