Whole Exome Sequencing – TRIO (Proband), Products of Conception (POC)
Use
WES is currently intended for use by patients suspected to have a genetic disorder. While the test is most frequently ordered for patients who have been unable to obtain a definitive diagnosis through traditional genetic testing, physicians may opt to initiate whole exome sequencing earlier in the diagnostic pathway. An initial workup using whole exome sequencing may be especially useful when a multigene testing approach is desired but would be prohibitively time-consuming, or when a known genetic disorder is suspected but testing for the genes of interest is not available. Patients with atypical presentation of a suspected syndrome may be candidates for exome sequencing. While patients can be of any age, many of the patients with the most pressing need for exome-wide interpretation are children with serious childhood genetic diseases. TRIO testing consists of a proband or patient sample, and both biological parents. In the case both parents are not available for testing, up to two family member samples are also accepted. TRIOs are preferred for better diagnostic sensitivity.
Special Instructions
Test orders include a prior authorization review, and there is a separate offering for prior authorization-only services using Test No. 630489. Maternal cell contamination testing is mandatory for fetal samples, and WES will not be conducted until this analysis is complete. If contamination is detected, the test will be canceled. Additionally, maternal blood should be submitted separately. For queries, contact genetic coordinators at 800-345-4363 before sending fetal samples.
Limitations
The incomplete understanding of the genome and variability in sequence data quality limits the results. A negative result does not rule out a genetic cause. This test can detect some mitochondrial DNA variants but not low-level heteroplasmic variants or large deletions. It does not detect mosaicism, CNVs, trinucleotide repeat expansions, or epigenetic changes. Sensitivity for insertions and deletions is lower than for substitutions. Some regions, especially those with repetitive elements or high similarity, may not be adequately evaluated. Hence, confirmation of diagnoses may not always affect patient management or improve outcomes.
Methodology
NGS (WES)
Biomarkers
LOINC Codes
- 86205-2
- 86205-2
- 56850-1
Result Turnaround Time
28-42 days
Related Documents
For more information, please review the documents below
Specimen
Other
Volume
10-15 mL amniotic fluid, 25 mg CVS, >2 to 4 mm(3) fetal tissue or two T-25 flasks of cultured amniocytes or cultured villi
Minimum Volume
5 mL amniotic fluid, 10 mg CVS, 2mm(3) fetal tissue, or two T-25 flasks cultured amniocytes or cultured villi
Container
Sterile plastic conical tube or two T-25 flasks
Collection Instructions
Flasks should be completely filled with media and cells should be ~90% confluent. Use sterile Ringer's lactate, Hanks' balanced salt solution, or Labcorp transport medium.
Storage Instructions
Sample should be shipped in an insulated container at room temperature or refrigerated.
Causes for Rejection
Flasks insufficiently filled; contamination; formalin-fixed paraffin-embedded tissue; tissue is not fetal in origin
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 2 - 3 days |
| Refrigerated | 2 - 3 days |
| Frozen | Do not freeze. |