Clinical Exome Sequencing:
Clinical Exome Sequencing is a test for identifying disease-causing DNA variants within the 1% of the genome which codes for proteins (exons) or flanks the regions which code for proteins (splice junctions). This test is intended for use in conjunction with the clinical presentation and other markers of disease progression for the management of patients with rare genetic disorders.
Even though there are over 2,000 Mendelian diseases caused by known DNA variants, many patients who are suspected or have been clinically demonstrated to have rare genetic disorders do not receive a molecular diagnosis, often due to genetic heterogeneity and the relative inefficiency of the current sequencing technology.
It is widely accepted that about 85% of known disease-causing variants occur within 1% of the genome containing the exons and splice junctions; thus, surveying just this portion of the genome is an efficient and powerful clinical diagnostic tool for individual patients.
Exactly how does exome sequencing work?
This genetic information is stored in DNA. The DNA is ‘housed’ in structures called the chromosomes. DNA is made of four chemicals or bases, represented by the letters A, T, C and G (adenine, thymine, cytosine and guanine). These bases form a unique sequence and changes (or variants) to this sequence can cause disease. A person’s entire genetic sequence is known as their genome.
Exome sequencing is a process that ‘reads’ the particular part of genes that are thought to be most important for health. These parts are called exons. These ‘reads’ contain large amounts of genetic sequence information, which would require hundreds of hours for a scientist to analyse manually. Computers are used to quickly identify variants in genetic information.
This list of variants is then ‘interpreted’ by comparing the results with databases that list variants known or suspected of being associated with genetic conditions. Interpretation is the most complicated and time-consuming component of exome sequencing because it involves input from many health professionals from different specialities to determine the significance of each variant detected.
What is Next Generation Sequencing?
Over the last few years, advances in next-generation sequencing technologies have decreased the cost of sequencing per base pair about 10-fold, improved accuracy, and significantly increased the speed of generating sequence data. Next-generation sequencing (NGS), also known as high-throughput sequencing, is the catch-all term used to describe several different modern sequencing technologies. These technologies allow for sequencing of DNA and RNA much more quickly and cheaply than the previously used Sanger sequencing, and as such, revolutionized the study of genomics and molecular biology.
What do my results mean?
Once your sample has been tested, a team of experts review any DNA changes or variants found. The team will determine the significance of any variants, using all the available published scientific literature.
Variants fall into a number of categories:
- Class 5: Pathogenic Variant
- Class 4: Likely pathogenic variant
- Class 3A: Variant(s) of unknown significance with high clinical significance
- Class 3B: Variant(s) of unknown significance:
- Class 3C: Variant(s) of unknown significance with low clinical significance:
- No variant of significance was found.
How to book an appointment for Clinical Exome Test?
You can call us at 04049171772 to book for Clinical Exome Test