This paper is a critical review of a position statement that discusses the impact of pharmacogenomics on individual drug effectiveness, specifically addressing the validity and sustainability of individual genotyping. The position paper identified three key issues regarding the validity of developing individual genotyping for drug effectiveness and a further four issues regarding the sustainability of developing individual genotyping for drug effectiveness. These are dealt with in turn below.
In terms of the validity of developing individual genotyping for drug effectiveness, one of the key issues is its ability to improve the health status of the individual. In theory, this is one of the main rationales for pharmacogenomics and Veenstraab & Burke (2009) identify areas such as oncology since the effectiveness of cancer treatments has been shown to be dependent on genetic variation, where pharmacogenomics may offer much promise in treating these individual variations. However, Eichelbaum, M., Ingelman-Sundberg, M., & Evans, W. (2006) note that a major drawback of the use of pharmacogenomics in a clinical setting is a limited number of clinical trials establishing the clinical validity or utility of pharmacogenomic testing in improving individual drug effectiveness. For this reason, Gurwitz, Zika, Hopkins, Gaisser, & Ibarreta (2009) argue that the potential impact of pharmacogenomics on individual drug effectiveness and its impact on social and economic variables remains unclear. Additionally, Veenstraab & Burke (2009) argue that the fact that pharmacogenomics can potentially improve the health status of the individual does not mean it would improve the health status of a population. This may be because those that may most benefit from pharmacogenomic guidance are likely to be those that are currently receiving sub-standard health care, but these are precisely the people that are least likely to be able to access this guidance (Veenstraab & Burke, 2009).
The second key issue is the ability of pharmacogenomics to allow clinicians to identify an individual’s reaction to medications to improve the accuracy of drug dosing and avoid adverse drug effects. This is a potential advantage in several areas such as in cancer treatments, where there tend to be adverse effects and variable responses associated with cancer chemotherapy (Veenstraab & Burke, 2009). Also, there are some drugs Warfarin, which can be fatal in normal doses to some people, can be prescribed more safely by using genetic testing to identify those individuals that need less of the drug (Veenstraab & Burke, 2009). However, Veenstraab & Burke (2009, p. 131) argue:
Though many gene variants are known to play a role, drug response is a complex phenomenon, influenced by factors such as diet, co-morbidities, and even other drugs. Thus, the predictive value of many potential pharmacogenomic tests remains small, and their clinical utility is generally not yet established.
The third key issue with regard to validity is the ability to create personalized medication plans for diseases and illnesses, as well as anticipate and prevent such diseases and illnesses. However, this may lead to negative repercussions for how tests and drugs are used in the interpretations of population differences in drug response are too crude. For example, Lee (2009) discusses the use of race as a substitute for genetic variation and argues that certain factors could lead to an “infrastructure of racialization” (p. 190).
In terms of the sustainability of developing individual genotyping for drug effectiveness, the first key issue is how to maintain patient privacy. Confidentiality of medical information is a fundamental principle in research ethics and the maintenance of this needs to be given top priority especially because research in genomics is often shared between academia and clinical fields, and the public and private sectors (Heeney, Hawkins, de Vries, Boddington, & Kaye, 2010).
The second key issue in terms of sustainability is cost-effectiveness. On a positive note, “testing costs for many well-known pharmacogenomic variants as well as genome-wide scanning are dropping dramatically” (Veenstraab & Burke, 2009, p. 132), which makes pharmacogenomics more accessible in terms of cost and more cost-effective. However, as with other areas in this rapidly developing field, the cost-effectiveness of individual genotyping has not been studied and therefore there is not much data available demonstrating favorable cost-effectiveness to support the use of pharmacogenomics in clinical settings setting (Gurwitz, Zika, Hopkins, Gaisser, & Ibarreta (2009).
Third, controllability and access to testing are important issues in terms of the sustainability of developing individual genotyping for drug effectiveness. On a positive note, access to testing has been boosted by improvements in the logistics of testing, as more people can directly access the service, and may even undertake genetic tests by mailing in their DNA (Veenstraab & Burke, 2009). However, proper planning and implementation must be done to ensure fair control and fair access to genetic testing thus regulatory measures must be in place for the control of genotype testing (Veenstraab & Burke, 2009).
Finally, as well as influencing the validity of developing individual genotyping for drug effectiveness, social determinants of health also impact the sustainability of developing individual genotyping for drug effectiveness. As previously noted, individual genotyping may not benefit populations in need of social and health policy reform because social determinants of health contribute to health disparities and inequalities. Thus those most likely to benefit from the improvements in pharmacogenomics and its impact on individual drug effectiveness are likely to be those most difficult to reach because of logistical, cultural, and other barriers and so the least likely to benefit (Veenstraab & Burke, 2009).
References
Eichelbaum, M., Ingelman-Sundberg, M., & Evans, W. (2006). Pharmacogenomics and individualized drug therapy. Annual Review of Medicine, 57, 119-137.
Gurwitz, D., Zika, E., Hopkins, M., Gaisser, S., & Ibarreta, D. (2009). Pharmacogenetics in Europe: Barriers and opportunities. Public Health Genomics, 12, 134-141.
Heeney, C., Hawkins, N., de Vries, J., Boddington, P., & Kaye, J. (2010). Assessing the privacy risks of data sharing in genomics. Public Health Genomics, 1-9.
Lee, S. (2009). Pharmacogenomics and the challenge of health disparities. Public Health Genomics, 12, 170-179.
Veenstraab, D. & Burke, W. (2009). Pharmacogenomics and public health. Public Health Genomics, 12, 131-133.