How Will Whole Genome DNA Sequencing Change Health Care?
There is a lot of excitement about advances in DNA sequencing and it appears we are on the cusp of including low-cost individual DNA sequencing as a routine part of individual medical care. While the massive amount of genetic information this technology provides is clear, it is not so obvious how this detailed gene sequence information might be practically applied to improve health care treatment.
In the future, when we have a much more thorough understanding of how a majority of human genes work and where the mutations are that produce malfunctions, this information will certainly prove very useful. However, in the near term when there is still so much about the function of genes we don't know, how useful will access to DNA sequencing be?
Two studies just published address this question and suggest the type of impact easily available DNA sequencing may have on medical diagnosis and treatment in just the next couple years.
Access to DNA Sequencing Would Improve Disease Diagnosis
Researchers at University of California's Rady Children’s Hospital in San Diego lead a study described in the June 13 issue of Science Translational Medicine that looked at 188 families with genetic history of brain developmental disorders such as epilepsy, autism, or intellectual disabilities. After screening out those with already known or obvious gene mutations related to the disorder, 118 families were left.
When they sequenced all the genes of individuals in the 118 families with a neurodevelopment problem, they found gene variations that affected family members had but others didn't, so they seemed to be related to the disorders. These gene mutations will obviously be interesting for further research.
The interesting thing from a diagnostic health care angle, however, is that, mutations associated with a neurological disease different than the one the family was diagnosed with were found in 10 of the 118 cases. In other words, DNA sequencing suggested a different condition than the medical record.
On review of the family medical history, the researchers concluded the diagnosis based on the DNA sequence was, in fact, correct, and the original medical diagnosis wrong. Actually, if these families had been correctly diagnosed, they would have been screened out of the study in the beginning when the researchers checked for mutations in known genes related to diagnosed brain and nerve disorders. Since the diagnosis was wrong, the researchers looked at the wrong set of genes for these 10 families.
From this study, DNA sequencing found that almost 10% of the cases for these brain and nerve disorders were misdiagnosed, which suggests that DNA sequencing will be a very reliable diagnostic tool for a whole range of genetic diseases. Also, this analysis was based on the current knowledge of which genes are involved in which diseases, which is very limited. As research continues and our understanding expands, the value of individual DNA sequencing for diseases diagnosing will increase exponentially.
Access to DNA Sequencing Can Improve Infectious Disease Treatment
The New England Journal of Medicine reported a study where investigators reconstructed an outbreak of MRSA (antibiotic-resistant Staphylococcus aureus) bacteria that occurred in a UK hospital neonatal intensive care unit in 2009.
The investigators from the Wellcome Trust Sanger Institute and University of Cambridge worked with the DNA sequencing company Illumina to sequence 7 MRSA strains that were associated isolated at the hospital around the time of the outbreak, then sequenced 7 MRSA samples that were collected from patients at various times during the outbreak.
Analysis of these DNA sequences from the collected samples clearly showed a cluster of patients that were involved in the outbreak with a specific strain. Also, they found an infection from one to another patient that was previously thought to be part of the main outbreak, but was a separate infection of another MRSA strain. Supporting this finding, a previous study in March from researchers at the University of Oxford ran a similar analysis of outbreaks MRSA and a another type of bacteria, Clostridium difficile, at a different hospital that also was able to chart the patient-to-patient transmissions.
Perhaps more importantly, however, in this recent JAMA study the researchers also used the DNA sequence of the bacterial genome to predict which antibiotics each MRSA strain should be susceptible to. They found a high level of correlation when they compared this predicted antibiotic susceptibility to the actual susceptibility profiles run during that outbreak.
The results show that, if high throughput DNA sequencing been available and used during the outbreak, the medical team would have been able to more quickly identify the source of the outbreak, the strain involved, and which treatment would be most effective to stem it.
Access to DNA Sequencing Will Very Soon Improve General Health
It is clear the advent of true personalized genomics is still some years off.
Also, although there is a lot of discussion about the predictive use of patient genetic information and even some current companies that purport to offer disease risk assessments based on gene sequence information, as a recent study suggests, we certainly don't know enough about genetics now to make any predictions other than for a very small number of specific diseases. The well detailed response to this study outlines very well the limits of our current understanding. Until our understanding of the underlying genetics has advanced further, it is really impossible to predict the long term utility and effect of gene sequencing on health care.
However, what is clear from the examples above is that, as soon as high throughput DNA sequencing reaches the point that is it routinely available for individual patient care, it will have an immediate and practical positive impact medical diagnosis and treatment.