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Peter Schwartz, MD, PhD., writes about the emerging importance of pharmacogenomics as well as current shortcomings in patients' understanding of pharmacogenomic testing results.

Dangerous Ignorance: What Patients Don’t Understand about Pharmacogenomics

Peter Schwartz, MD, PhD. Director, IU Center for Bioethics

Do you know what pharmacogenomics is? You might not, but you should, and all patients should. Pharmacogenomics (pronounced pharma-co-genomics), which we’ll abbreviate PGx, may well be the first type of genetic testing you will get. PGx checks for genes that interfere with the body’s response to certain medications, either reducing their effectiveness or increasing side effects. For instance, some people have a gene that stops a blood thinner called clopidogrel (or “Plavix”) from working. The result can be dangerous or even life threatening since clopidogrel is often prescribed to to keep blood flowing through cardiac stents that have been recently placed. Some people have a gene that makes common pain killers like codeine or hydrocodone more potent, potentially causing an overdose at even a low starting dose. If a provider knows that their patient has one of these genes, they can prescribe other medications or adjust the dosage.

Over 250 medicines currently have PGx testing listed on their FDA-approved labeling. One study found that 63% of adults and 29% of children with pharmacy insurance coverage were prescribed medicines that were significantly affected by their genes (Liu et al. 2021) . Another study predicted that 99% of over seven million veterans had at least one genetic variant that could affect how medicines work for them. (Chanfreau-Coffinier et al. 2019).   

PGx testing is not yet common in health care, though, for a number of reasons. One challenge is its price and getting insurance to pay for it, despite some evidence that PGx in the right settings could save money in the long run. Another big barrier is getting the results to providers and teaching them how to interpret the results and respond.  

Another barrier is teaching patients about their test results and what they mean, so they will know which medicines they can’t take or should take differently from other people and why. Our team, led by Tom Doyle, PhD, a post-doctoral fellow at IUCB, and me just published a paper that studied, for the first time, how well patients understand the results of their own PGx testing. The paper appears online in a journal called Patient Education and Counseling and can be accessed for free here. (full citation in endnote) 

Here's the story: Thanks to a program funded by the IU Precision Health Initiative, patients at IU Health who are having cardiac catheterization now get tested for the CYP2C19 gene, the one that can change the effectiveness of clopidogrel (Plavix). Providers get the results through the electronic health record, and patients are sent a brochure, letter, and wallet card telling them about the result and what it means. Our team interviewed 31 patients to assess whether they know what PGx is, that they had PGx testing, and what their results are, including what the results could mean for their future healthcare.  

The bottom line is that, sadly, the patients we interviewed didn’t know much. Only 4 of the 31 (13%) recognized the term “pharmacogenomics” and were able to give an acceptable definition of it. After being told what PGx is, only 10 of the 31 (32%) knew they had undergone this sort of testing. None knew the name of the gene that was tested, but 7 (23%) knew whether the result indicated that there are some medicines that might have lower effectiveness or unusual side effects. Four additional patients (13%) had saved the letter or wallet card and looked at it to tell the interviewer what the testing had shown. While only 10 participants (32%) remembered receiving the brochure, letter, or wallet card, these patients gave these materials high ratings. At the end of the interview, many patients said they wanted their future providers to have their PGx results and wanted to understand them as well.

So, what’s the take home message? In short, healthcare professionals have to do a better job of educating patients about PGx, especially as it becomes more and more a part of everyday practice. It’s essential to get the information to providers, as some experts at IU School of Medicine are doing, using the electronic health record, and it’s essential to teach providers about PGx. PGx will only happen broadly if insurance companies to pay for it.  

But it’s also essential to find ways to educate patients about what PGx is and what the results mean for their personal, individual health. Whatever systems are in place to get the information to providers, there will be times when these systems fail, and then lives are on the line, since patients could be prescribed medicines that the testing already showed will not work or could even be dangerous. This is particularly important as people move from place to place, and switch health systems, and electronic health records fail to talk to each other.  

How could patients be educated better? One possibility is telling them more about PGx at the time of their testing and making sure a provider or staff member talks to them about the results afterwards. Providing a letter or wallet card, or some electronic reminder or link – such as a QR code, or something on a patient portal of the electronic health record – could also help.  Even if patients do not always understand the results, they could tell their providers that they were tested and help them find the results.

I’m proud of our team for clarifying the limits of patient understanding in this area and pointing the field towards the challenge of doing better at educating patients. This is a great example of how increasing patient engagement and understanding is so important to improving care, even as it is so challenging. Our team will continue to work in this area, where improving patient understanding can save lives.

This blog was written in reference to:

Doyle TA, Schmidt KK, Halverson CME, Olivera J, Garcia A, Shugg TA, Skaar TC, Schwartz PH.  Patient understanding of pharmacogenomic test results in clinical care.  Patient Education and Counseling. Free Access Link:

The views expressed in this content represent the perspective and opinions of the author and may or may not represent the position of Indiana University School of Medicine.
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Peter Schwartz, MD, PhD

Peter H. Schwartz, MD, PhD, is the director of the IU Center for Bioethics and associate professor of medicine at IU School of Medicine.