X-Chromosome Inactivation Analysis
Also known as: XCI
Use
This test is used to determine the X-chromosome inactivation (XCI) pattern for female carriers of X-linked disorders. It helps assess the potential pathogenicity of a genetic variant in an X-linked gene, although it does not detect clonality. The pattern of XCI can provide insights into skewed or random inactivation which might occur due to various genetic or environmental factors.
Special Instructions
Testing is limited to XX females only and requires informed consent, especially for patients from New York state. Consents are to be managed by the ordering physician. Submit a Non-Permitted Laboratory Request Form to NYDOH if necessary.
Limitations
The test is informative for XX females only and may be uninformative in up to 20% of individuals due to homozygosity at the androgen receptor gene locus. XCI patterns can differ among tissue types, making it important to note that results pertain to the tissue type tested. The test will not determine if the XCI pattern is linked to X chromosome rearrangements, pathogenic variants in X-linked genes, or neoplastic disease, and is not suitable for prenatal diagnosis. It is subject to limitations due to rare sequence variations.
Methodology
PCR-based
Biomarkers
LOINC Codes
- 66746-9
- 35455-5
Result Turnaround Time
10-14 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
2 mL
Minimum Volume
1 mL
Container
Lavender (EDTA), pink (K2EDTA), or yellow (ACD solution A or B)
Storage Instructions
Refrigerated. Also acceptable: Ambient.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 1 week |
| Refrigerated | 1 month |
| Frozen | Unacceptable |