Next Generation Sequencing (NGS)
technology allows to realize different types of analysis; among them we can
inquire more and more inside the human genome, proteins, metabolism and
diseases. Thus, the analysis of exome with high accuracy is possible nowadays.
The exome is the portion of our genetic material, DNA, that is encoded to
proteins which are going to enter into our metabolism, so the exome analysis is
a powerful tool in health since it is direct related to development of the
human body.
Dixon, alongside his team, performed
a survey where the objective was to explore NGS's implications in public health,
particularly exome sequencing. For its investigation, they focused on
neuro-developmental disorders for various reasons. Firstly,
neuro-developmental disorders affects to
6% of the population approximately, and it has consequences on intellectual
capability, epilepsy, autism, and muscular disorders. Secondly, these disorders
are complicated to diagnose because it is difficult to get an neural tissue
sample; consequently, almost 10.000$ per patient are spent in evaluations, and
it represents up to 10% of the total US Center for Diseases Control's annual
budget. Finally, health investigators observed that these diseases exhibit both
clinical and genetic heterogeneity that makes them perfect for the use of
certain genetic analysis.
In this project, investigators
realized an whole exome sequence (WES) of 118 persons. In order to get the best
representation of human population as they could, people with high levels of
consanguinity were sampled, to increase the power of detection for some
uncommon genes. Aditionally, they must have been diagnosed with a
neuro-developmental problem or been related to some person with the disorder.
The WES analysis provides some interesting results: common and obvious
disorders could be diagnosed, a set of genes related to developmental
abnormalities were discovered, and; in the rare case disorders, a pre-natal
diagnosis possibly method was suggested. In contrast, WES is less accurate than
it was expected due to incongruence on disorder's description, incomplete
medical history, or non-clinical features present in patients possibly. Finally,
the cost of the analysis was calculated between 2000$ and 4000$.
In summary, WES and other NGS
technologies are important tools for diagnosis for neuro-developmental
disorders, and rare case development problems in general. Although these
technologies present some limitations, they represent a support to find
disorders in human population. Furthermore, the greatest input of these new
methods is the economic cost, 4000$ is greatly lesser than the amount that is
spent in a single patient nowadays, and this value is tending to be less and
less with the development of more powerful and trustable sequencing technology.
References
Dixon-Salazar, T. J., Silhavy, J.
L., Udpa, N., Schroth, J., Bielas, S., Schaffer, A. E., ... & Gleeson, J.
G. (2012). Exome sequencing can improve diagnosis and alter patient management.
Science translational medicine, 4(138), 138ra78-138ra78.
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