Critical to the idea of precision health is the notion that a patient’s DNA can guide their clinical care. In recent years, researchers have brought us closer to this ideal by identifying genetic variants that influence how patients respond to medications. With this information, pharmacogenomic assays have been developed to help physicians screen their patients’ DNA to provide more informed and personalized treatment. To reduce the cost of these tests, assays are designed to cover the most common and informative variants. However, what’s considered common and informative is dependent on a person’s genetic ancestry, and the majority of pharmacogenomic research is focused on people of European descent1. Addressing disparities in healthcare is a priority for many health systems, but pharmacogenomics is an area that’s impact has been overlooked.
Only 13% of pharmacogenomic genome-wide association study participants are of African, Asian or Hispanic descent.
In a recent review of pharmacogenomic genome-wide association studies, it was found that 78% of included participants were of European descent, while African, Asian, and Hispanic ancestries were collectively represented by just 13% of studied participants2. As a result, there is a growing precision health disparity wherein patients with European ancestry benefit the most from genetic research.
This disparity in representation has significant implications for the effectiveness of pharmacogenomic screening in patients from diverse backgrounds. Recently, Helix researchers published findings from a large survey of variants in pharmacologically relevant genes using data from a diverse collection of >80,000 research participants3. The team found that out of the 152 variants that were classified as rare amongst those with European ancestry, 16 variants were actually 10 fold more prevalent in at least one other ethnicity.
For example, clopidogrel is a blood thinning drug that is commonly prescribed to prevent heart attacks and strokes. Genetic research has shown that a variant in the CYP2C19 gene (known as CYP2C19*3) can stop blood-thinning drugs, like clopidogrel, from working. So knowing if a patient has this variant should significantly impact what a physician prescribes to protect them from dangerous blood clots. However, while this variant is only found in 0.02% of participants with European ancestry, it’s incidence is approximately 7.4% in patients of East Asian descent. If a pharmacogenomic test were designed based on the current dataset, this seemingly rare variant would likely be excluded, disproportionately impacting patients of East Asian descent.
Research like this is a significant step towards overcoming disparities in precision health. Two important factors that impact the ability to provide equity in pharmacogenomics are: 1) the clinical assay itself and 2) the ability to integrate this information into clinical care. At present, clinical assays likely miss variants like CYP2C19*3 that are of high prevalence and consequence in non-European ancestral populations because these panels are designed to cover the most commonly known variants. According to Helix’s research, typical commercial pharmacogenomics assays may mis-genotype as much as 17% of samples owing to their narrow focus3. By highlighting the variation that occurs across ancestral backgrounds, we can work towards a more equitable model for precision health in clinical settings.
Doing so is no easy task, however. Variations in pharmacogenetics are not always simple base substitutions, they can be structural or gene duplications that are very challenging to detect. To truly interrogate the complex architecture of pharmacogenes, assays have to be high-resolution and supported by custom bioinformatics solutions like Helix’s Exome+ sequencing assay and pipeline.
40% had a high risk of experiencing adverse affects from medications they had already been prescribed.
Integrating comprehensive pharmacogenomic screening into clinical care is an important step towards expanding access to precision health because it enables physicians to prescribe potentially more effective and less harmful therapeutics, regardless of their patient’s ethnicity. At present, many patients do not have access to this level of care. In our study, Helix researchers assessed electronic health records in a subset of 30,000 participants from the Healthy Nevada Project. This analysis showed that as much as 40% of the cohort had a high risk of experiencing adverse effects from medications that they had already been prescribed, underscoring the need for proactive pharmacogenomic screening.
Fortunately, proactive screening for pharmacogenetic variants is not just something coming in the theoretical future—it’s already possible today. Helix is supporting many of the nation’s largest population genomic programs through which patients consent to be sequenced using the Exome+ assay. The data generated from these studies is securely stored and, given the proper consent, can be revisited by healthcare providers to screen patients for pharmacogenomic variants and other clinically relevant findings—a model that’s known as Sequence Once, Query OftenTM. One round of sequencing with Helix’s high-quality assay provides a wealth of data that can be used to rapidly answer a myriad of questions at the point-of-care throughout a patient’s lifetime. For pharmacogenomic testing, this means there’s no need to order a new, time-consuming round of sequencing; physicians can quickly screen the patients data for relevant variants and tailor the patient’s treatment accordingly, while they are sitting in front of them.
Ensuring that you are working with a lab that has the ability to support large-scale proactive genetic screening, and the ability to detect complex pharmacogenomic variants across ancestral backgrounds, will be critical to creating an equitable future in precision health for your community.
To deep dive into the science and learn more about pharmacogenomics, watch our webinar with Genxys now.
1. Luczak, Tiana et al. “Applying an equity lens to pharmacogenetic research and translation to under-represented populations.” Clinical and translational science vol. 14,6 (2021): 2117-2123. doi:10.1111/cts.13110
2. Sirugo, Giorgio et al. “The Missing Diversity in Human Genetic Studies.” Cell vol. 177,1 (2019): 26-31. doi:10.1016/j.cell.2019.02.048
3. Luo, Shishi et al. “Comprehensive Allele Genotyping in Critical Pharmacogenes Reduces Residual Clinical Risk in Diverse Populations.” Clinical pharmacology and therapeutics vol. 110,3 (2021): 759-767. doi:10.1002/cpt.2279