Whole Exome Sequencing – TRIO (Proband), Products of Conception (POC)

Casandra

Casandra Test Code LC98636Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 630979CPT Codes 81415, 81416

Whole Exome Sequencing – TRIO (Proband), Products of Conception (POC)

Clinical Use

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.

Test Details

Methodology

NGS (WES)

Biomarkers

Whole Exome Sequencing analyzes the patient's entire exome to identify genetic variations that may explain the patient's condition. It includes the sequencing of the exomes of the proband and both biological parents.

Whole Exome Sequencing • WES

LOINC Codes

Order Codes

86205-2

Result Codes

86205-2
56850-1

Result Turnaround Time

28-42 days

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.