In time, personalised medicine tests will not only include tests of genes, but also tests of proteins, RNAs and other important biomolecules. Currently, however, most of the attention is focused on developing genetic tests. These tests are based on the fact that the sequence of a typical human gene is as variable as any other human trait. Just like heights and hair colors, different people often have slightly different sequences for any given gene. Because your genes make your proteins, when two people have different sequences for a gene, they may also have different levels of activity in the protein that gene makes. One reason you possess your unique combination of physical, emotional, intellectual and medical characteristics is that you possess a unique pattern of high activity in some proteins, typical level of activity in others, and low level of activity in others.
Because your genes make your proteins, you can often estimate the level of activity the person will have in a protein by analyzing the sequence of the corresponding gene. Further, because your proteins regulate all your body's systems and processes, if you know the level of activity in the critical proteins, you can estimate how well a particular system works in the individual. This in turn enables you to estimate that person's risk for the diseases that result if the system in question is not working well. For example, if you know the sequence of the genes that make the proteins that act as ion channels in heart muscle, you may be able to estimate the individual's risk for certain cardiovascular (heart) diseases more accurately than you could otherwise. Alternatively, if you can estimate the level of activity in the proteins that break down a specific drug and clear it from our bodies, you can better predict the probability that a particular person will accumulate too high a concentration of the drug and have an adverse reaction to the drug if he/she is given the dose of that drug that most people are given.
This approach to medicine is referred to as Personalised Medicine (PM), because it allows the doctor to consider the individual patient according to his/her personal characteristics, rather than treat everyone who has a particular disease with the same drug and dose. PM does not only aim to allow doctors to treat patients more safely and effectively. PM also expects people to play a more active role in maintaining their own health than most of us are accustomed to playing. Dr. Leroy Hood helped coin the term "P4 Medicine". The four "Ps" refer to PM being personal, predictive, preventive and participatory. One of the cornerstones of this approach is the understanding that our genetic risk factors interact with risk factors we encounter from our diet, environment and lifestyle to determine our overall risk for a disease. Knowing what diseases you have the highest genetic risk for enables you and your doctor to estimate your risk for diseases more accurately (personal and predictive). In addition, it may help some people tailor their diet, environment and lifestyle, to actively “participate” in maintaining their own health and well being (preventing disease) and try to avoid some of the factors that may further increase their risks for these diseases.
People's access to genetic/genomic information and the role it can play in their lives will continue to expand. At present the cost of many genome sequence tests remains high enough to be out of many people's reach. The cost, though, will continue to drop dramatically, and it will soon be possible to obtain a person's entire DNA sequence for less than $1,000. This of course does not come without its own set of challenges. At present, we do not understand exactly how to translate most of the information that is obtained through genetic tests into risk predictions or treatment recommendations. Because of the sheer number of genes that influence our risks for most diseases, and the complex nature with which they interact with each other and with nongenetic factors, there is still a great deal of research that needs to be done in order to enable doctors to use our genetic information to improve the practice of medicine. The genetic information must be considered in the context of one’s personal and family history, as well as one’s age, sex and medical data (such as blood sugar level).
The ability to obtain this kind of information also carries with it substantial psychological challenges. Some people would rather not know the results of a genetic test if the result may indicate that they have an increased risk for a disease for which there is no effective treatment, such as Alzheimer disease. Genetic counselors help with all aspects of the genetic testing process. A genetic counselor can inform you about the tests that are available, discuss the benefits and limitations of the available tests, help you interpret the information provided by the test and help you cope with the psychological and family issues that may arise.
We are on the brink of a remarkable revolution that promises truly personalised medicine. PM tests will help you better understand your genetic risks, and allow you to become more involved in maintaining your own health and well being by focusing on the environmental and lifestyle factors that are most likely to make your sick. There will also be a change in focus, from an emphasis on treating disease to an emphasis on maintaining health. Before the end of this decade, people will have access to a great deal more information than they have access to now. In order to reap the greatest benefit from these new medical advances, it is critical that you understand how to interpret your genetic information, and what the potential benefits and limitations of the available genetic/genomic tests are.
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