Horizon Genetic Carrier Screening Test
What is the Horizon carrier screening test?
The Horizon™ test uses various methods to identify carriers of different types of genetic variants: NGS sequencing (with complete analysis of the coding sequences of genes rather than only the most common mutations); copy number analysis; PCR (Asuragen) to determine repeat sizes, etc. These methods are often used in combination to increase the sensitivity of the test. In addition to broad screening coverage, Horizon™ provides greater depth of analysis for specific conditions. Confirmation by Sanger sequencing is also mandatory.
Features of the Horizon™ test for specific conditions:
CYSTIC FIBROSIS – Horizon™ analyzes more than 500 clinically significant variants associated with the disease and identifies 23–34% more carriers than standard genotyping-based panels. Clinically, this means a higher carrier detection rate.
SPINAL MUSCULAR ATROPHY – Horizon™ can identify silent carriers (up to 8% of cases): using SNP technology, the Horizon™ test determines the number of SMN1 gene copies on each chromosome of the pair. This is important for detecting silent carriers of spinal muscular atrophy, in whom two copies of the SMN1 gene are located on one chromosome and no SMN1 copies are present on the other chromosome (2 + 0 SMA). Standard screening methods miss 5–8% of silent carriers.
FRAGILE X SYNDROME – Horizon™ can detect both a full mutation of the FMR1 gene (more than 200 CGG repeats) and premutation alleles (50 to 200 CGG repeats), as well as the presence of AGG interruptions within the mutant allele sequence. A greater number of AGG interruptions reduces the risk of CGG repeat expansion. Most standard tests report only the number of CGG repeats present in the patient. Horizon™ automatically includes AGG interruption testing for patients with 45–90 CGG repeats
When can the test be performed?
As part of preconception preparation for couples planning a pregnancy.
Benefits:
- If the test shows that you are a carrier of one or more genetic disorders, you may have an increased risk of having a child affected by these conditions. The risk of a child developing the condition depends on the following factors:
- In most cases, your partner must also carry a disease-causing variant in the same gene. Even if both of you are carriers of the same autosomal recessive disorder, there is a 25% chance of having an affected child.
- If you are a woman and a carrier of an X-linked disorder (involving a gene located on the X chromosome), each son has a 50% chance of inheriting the affected X chromosome, while each daughter has a 50% chance of inheriting it and may be a carrier or affected by the condition.
- Carrier screening for disorders affecting the X chromosome is offered only to women.
If you and your partner are at risk of having a child with one of these conditions and you are not currently pregnant, you may consider pregnancy through IVF (in vitro fertilization) with genetic testing of the embryos. This is called preimplantation genetic testing for monogenic disorders, abbreviated as PGT-M.
Required biological material:
- Venous blood