By Douglas L. Brutlag

The impact of genomics on health care

Since the determination of the sequence of the human genome, there have been numerous implications for patient health care. Most notable among them are new and more accurate diagnostic tests for inherited diseases, determination of the best drugs with the least side effects for patients, early detection of inherited diseases based on non-invasive prenatal maternal blood tests, prenatal genetic selection to avoid passing on debilitating or lethal inherited diseases and even estimations of a person's risk for complex diseases that have both genetic and environmental causes.

In addition to these patient-specific impacts, genomics has provided many novel drug targets for the pharmaceutical industry and discovery of genes and mutations in them that directly cause disease, leading to new diagnostic possibilities. Genomics has had and will continue to have a major impact on patients' healthcare, physicians' practice, drug discovery and basic scientists hoping to understand and cure inherited diseases. Because the field is developing so rapidly, with new diseases, diagnostics and drugs being discovered daily, it is essential that patients and physicians be educated on the importance of these results for healthcare. It also requires more medical students to specialize in medical genetics and a larger number of people to be trained in genetic counseling to advise patients about genetic diagnoses and how to help them interpret the meaning of the results to improve their healthcare.

Genomics as the basis of preventive medicine

The most important aspect of genomics is that it forms the basis for preventive medicine for inherited disease. Just as vaccines have had a major impact on preventing infectious disease, genomics has the potential to permit the prevention of inherited diseases. As Louis Pasteur, the discoverer of man-made vaccines and the godfather of preventive medicine said, "When I think about a disease, I never think about how to cure it, but instead I think about how to prevent it." Prevention of an infectious disease requires knowledge of the causative agent (usually a virus or bacteria) and the development of a vaccine against it. Prevention of an inherited disease requires identification of the genes and mutations causing the disease and followed by either a treatment or drug targeting these genes. The study of the genetics of patients, families and populations afflicted with an inherited disease reveals the nature of the genes and their mutations that cause the disease. With these genes and mutations in hand, we immediately have a good diagnostic tool for detecting and characterizing the disease, and these discoveries direct further research that will lead to novel treatments, interventions and drugs that specifically attack the cause.

When attempting to prevent a disease, one must first know the cause and then develop appropriate treatment just as Pasteur did for infectious diseases. Most often, our treatment of disease is targeted at ameliorating the symptoms rather than attacking the cause. When one tries to treat the symptoms instead of the cause, one often exacerbates the disease itself, which continues unabated. Since the basis of many inherited diseases is contained in our genetic information, some of these diseases can best be treated genetically via either gene therapies or via stem cell approaches. Complex diseases (those that have both a genetic and an environmental cause) can be treated by changing the environment or the behavior of the patient.

The best description of the importance of preventive medicine I have read was written in the first Chinese Medical Textbook in 2600 BC: "Superior doctors prevent the disease, mediocre doctors treat the disease before it is evident to the patient and inferior doctors treat the full blown disease." Our current healthcare system does not care for the healthy, but instead treats the ill. Maybe it should be renamed our illness care system rather than healthcare system. We need to develop policies and incentives to keep patients out of the hospital and out of doctor's offices. We know that preventive medicine can greatly reduce the cost of healthcare. It has been determined that every dollar spent on prevention saves ten dollars in treatment. An unfortunate corollary to this is that there is more of a market for treating the ill rather than preventing illness. Treatments bring more profits than prevention; drugs bring more profits than vaccines.

Genomics has the potential to develop diagnostics that can inform a patient of their risks as well as new treatments and interventions that can attack the cause of their disease, including drugs, gene therapies and stem cell approaches.

Personalized medicine

Another major impact of genomics is that it permits a highly personalized form of healthcare. For example a simple genetic test can tell you how you will react to different drugs, what an appropriate dose is for you and whether you are likely to have adverse reactions to them. The FDA currently requires 107 different drugs be labeled if a genetic test is either required or recommended prior to prescribing them. This area is called pharmacogenomics and is one of the most useful areas of the application of genomic information.

Similarly your genomic information can not only tell if you are a carrier of a highly penetrant mutation for a Mendelian disease, but what your risk is for more complex diseases which may only have a 25 to 50% genetic component. These risk estimations are most important because changing the environment or behavior can reduce the risk indicated by ones genetics. It can increase one's vigilance and often suggest additional follow up clinical tests to see if such a complex disease is progressing or not.

Sir William Osler, considered the father of modern medicine, said in 1892: "If it were not for the great variability among individuals, medicine might well be a science, not an art." Personalized medicine based on genomic tests holds the promise of making medicine a true science. More importantly it shows how irrelevant anecdotal information should be to patients. Just because a drug works on your neighbor's afflictions, does not have any relevance to how the drug will work on you. Only your genetic background can inform you of the best treatment. The goal of personalized medicine, according to the FDA, is to give the right drug to the right patient at the right time.

Adverse reactions to genetic tests

While there are many positive aspects of genomic and genetic tests described above, there are some adverse reactions to such testing that are equally important as well. This is particularly true for inherited diseases which have no cure and which are invariably fatal such as Huntington's disease. Genetic testing has been shown to give rise to adverse reactions such as suicide, attempted suicide, depression, divorce, isolation and other behavioral disorders as often as 26% of the patients. Less penetrant genes such as BRCA1 and BRCA2 that can lead to an 80% life time risk of a series of different cancers. It is important that a patient meet with a genetic counselor prior to undertaking any such test so as to maximize the usefulness of the tests to the patient. It is critical to determine what the patient's reaction to both a negative and a positive finding will be so that the path forward is clear to both the physician and the patient. The increasing use of genetic tests in healthcare will require a very large increase in the number of highly trained genetic counselors.

Genomic education is an ongoing process

Finally, it is also increasingly important that both physicians and the public be made aware of the progress and limitations of genetic testing. Many of the concepts discussed above, (inherited diseases, Mendelian diseases, complex diseases, genetic tests, pharmacogenomics, risk estimation) are not commonly understood and most often misunderstood. There is a very important need for books, courses, tutorials, websites, videos and journal articles to explain these concepts to the public. The field is moving so quickly that one cannot keep up without understanding the underlying concepts. As more and more diseases can be diagnosed and treated based on genetic tests, understanding the basis of genetic disease and their treatments will be more and more essential for both clinicians and patients.

It is also critically important to not only train medical students in the same area, but also to provide continuing education opportunities for existing physicians so that they can interpret genetic results just as they would any other clinical test. They must know what each test can tell you about a disease, when it is appropriate to order such a test and finally what clinical follow-ups should be done to confirm the genetic results.

I have been teaching premedical students a course in Genomics and Medicine for the past 12 years, and our medical school has been training all its students in genomics and personalized medicine for the past four years. More recently I have also taught a Stanford Continuing Education course entitled "Your Genes and Your Health" for the public. Both my courses are freely available online where one can download videos and slides of the lectures and watch them on your own computer. In the references below, I give a list of books, courses, websites and personal genomics firms that will help educate both patients and physicians in this exciting new area of medicine. 


Douglas L. Brutlag, PhD, is Professor Emeritus (by courtesy) of Biochemistry and Medicine, Stanford University School of Medicine.


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