What is Trio Whole Exome Sequencing?
Trio Whole Exome Sequencing (WES) is a highly complex test that is developed for the identification of changes in a patient's DNA that are causative or related to their medical concerns. In contrast to panel sequencing tests that analyze one gene or small groups of related genes at a time, WES will analyze the exons (coding regions) of thousands of genes simultaneously using next-generation sequencing techniques.
The exome refers to the portion of the human genome that contains functionally important DNA sequences that direct the body to make proteins essential for the body to function properly. These regions of DNA are referred to as exons. There are approximately 180,000 exons in the human genome which represents about 3% of the genome. These 180,000 exons are arranged in about 22,000 genes. It is known that most of the errors in DNA sequences that then lead to genetic disorders are located in exons. Therefore, sequencing of the exome is thought to be an efficient method of analyzing a patient's DNA to discover the genetic cause of diseases or disabilities.
This test sequences the exome nucleotide by nucleotide, to a depth of coverage necessary to build a consensus sequence with high accuracy. This consensus sequence is then compared to normal population standards and references, and the result is interpreted by board-certified laboratory directors and clinicians. By sequencing the exome of a patient and comparing it to normal reference sequence, variations in an individual's DNA sequence are identified and associated with medical conditions.
Parental samples are required to interpret Trio WES results. See below and requisition for sample requirements and further details. Testing cannot be requested unless both parents submit samples for testing. Separate parental reports will be issued.
Indications for Testing
• Patients with a history of multiple congenital anomalies, autism spectrum disorder, neurodevelopmental disorders, developmental delay, intellectual disability, failure to thrive, dysmorphic features, and/or epilepsy syndromes
• Patients with an extensive differential diagnosis
Special Note
If a qualified variant is found by this test, RNA sequencing (RNAseq) can be performed to aid in the reclassification of the variant. A qualified variant meets our prediction algorithm criteria (SpliceAI) that RNAseq will provide additional functional information.
Select RNAseq at the time of order to reflex to RNAseq if a qualified variant is found by WES. RNAseq can only be performed on blood samples; if an additional sample is required to perform RNAseq, Client Services will reach out to the ordering provider.
Limitations
The interpretation of nucleotide changes is based on our current understanding of the specific genes. This interpretation may change over time as more information about these genes becomes available. Possible diagnostic errors include sample mix-ups, genetic variants that interfere with analysis, incorrect assignment of biological parentage, and other sources. Please contact a genetic counselor at Baylor Genetics if there is reason to suspect one of these sources of error.
21 days
Turn Around Time