Genetic testing for better health

Healthy ageing, the prospect of living a healthy, prolonged life, can be considered one of the goals of healthcare in the 21 st century. For my PhD research, I investigate how genetic testing can help individuals receive personalised treatment options in complex diseases, such as depression and diabetes.

_{By Taichi Ochi / Pictures: Henk Veenstra}

Factors for healthy ageing

There are many factors at play to achieve healthy ageing. Currently, the consensus seems to be that being physically active, maintaining a healthy weight and eating a balanced diet, are all important considerations. However, there are also factors at play which we are unable to have any say in but can use to help us make better decisions to achieve healthy ageing.

Personalising medicine through genetics

The completion of the Human Genome Project has opened the pandora’s box on the understanding of the role of genes in the human body. The project was successful in sequencing the human genome. One of the milestones achieved was the unravelling of genes that play a role in drug response. Not only were these genes categorised, the opportunity to sequence genes more accessibly opened the door for enabling genetic testing to enter as a potential healthcare tool.

Targeting the pharmacogenetic variants

Pharmacogenetic variants are variants in genes which play a role in the variability of drug response. Guidelines outlining interactions of these pharmacogenetic variants have been established, for the so-called ‘drug-gene interactions’. These guidelines provide a framework for healthcare practitioners to use to improve medication prescription to patients. It could be reasonably considered that further research in this field should build towards the implementation of the guidelines into practice and focus on expanding the guidelines. Nevertheless, questions remain on whether the tests can be considered cost-effective and have utility in practice.

Defining the cost-utility of genetic testing

Health economic evaluations aim to compare the costs and effects of interventions. For genetic testing, the health economic evaluation would look to determine if the genetic test would reduce the costs of treating a disease. For established drug-gene interactions, a strong case for conducting pre-emptive genetic testing has been established, where patients can avoid ineffective treatment or adverse reactions. With reducing costs of genetic testing, it would seem that the cost-effectiveness of these tests is guaranteed. However, targeting these drug-gene interactions only is part of the picture for utilising genetic testing for personalised treatment. What if we could understand the risk of disease in individuals through these genetic tests? Enter genetic risk scores.

Expanding the case for genetic risk scores

Genetic risk score, also known as polygenic risk score, provides an individual the risk for getting a disease. Understanding one’s genetic risk may help improve an individual’s outcome in developing a disease. For single-gene diseases, mutations in one gene can cause the disease (e.g. cystic fibrosis and CFTR gene), whereas for complex diseases, such as heart diseases and diabetes, multiple genes have been found to be associated with the disease. Therefore the value in generating genetic risk scores for complex diseases would help individuals better understand one’s risk to getting the disease and look to take steps to avoid complications. Yet, consensus on which genes to target or whether it would a cost-effective measure to avoid disease progression has not been reached.

Targeting personalised treatment for depression

One such complex disease that piqued my interest was depression. Although social stigma has decreased for mental health in recent years, it is still a hurdle of struggling individuals to achieve optimal treatment. There are multiple options to treat depression, with taking antidepressants being one of them. My interest in depression lies in the applicability of genetic testing for improving patient outcomes. Antidepressants have many known drug-gene interactions therefore validating the utility of pre-emptive genetic testing would help ensure patients receive the optimal medication and dosage. With genetic risk scores, it would be interesting to determine whether categorising individuals to risk profiles would improve treatment for the individual. For example, individuals with high risk would benefit from receiving earlier treatments, such as counselling and cognitive behavioural therapy. By providing such tools, the aim would be to empower patients to be able to better understand their condition and make decision to empower their lifestyle.

Determining long-term impact

Genetic testing may sound like it would improve treatments, one of the issues is regarding the cost over the genetic test. Over the years, numerous economic evaluations of genetics have been conducted but have yielded mixed results. One reason may be that for earlier studies, the cost of a genetic test was high. With the cost of genetic testing decreasing and accessibility these tests to individuals grows, a shift in outcomes of the evaluations have changed. One area where I see a gap in these evaluations is that most of them take into consideration only a single drug-gene interaction. However, an individual may be faced with multiple drug-interactions over one’s lifetime. Therefore, I believe economic evaluations need to take a long-term focus in an individual’s life where a genetic test may be effective in determining risks of complex diseases for managing one’s health.

Delivering personalised medicine

My upcoming research is to evaluate whether pre-emptive genetic testing would be deemed cost- effective over the long-term study period. The PharmLines Initiative combines individual information from LifeLines with the prescription database, IADB.nl, to provide the information necessary to conduct the study. To determine the economic value of genetic testing, it is important to know how often certain pharmacogenetic variants occur in the population. More importantly how often they occur in individuals using the interacting medication. I hope that my research helps chisel away the uncertainty regarding implementing genetic testing as a pre-emptive tool to optimise healthcare and facilitate healthy ageing.