Several studies have assessed general public interest in disease susceptibility genetic testing,^4–9 though only a handful of studies have assessed the public’s perspectives of PGx testing, most of which have been on European populations. For example, studies from Germany and the U.K. report that the public are generally supportive of PGx testing but expressed concerns regarding patient sovereignty, the unavailability of suitable drugs based on genetic make-up, and privacy.^{10, 11} Participants of an Iceland study were concerned that genetically tailored drugs would be more costly and result in greater health disparities.¹² It is uncertain whether differences in the healthcare systems and coverage and reimbursement as well as concerns about genetic discrimination between the U.S. and Europe would yield differences in public support for PGx testing in the U.S.

The saliency of these issues were partially confirmed in three focus group studies conducted in the U.S. explored public attitudes toward PGx testing within the framework of drugs targeted to a patient’s race.^13–15 One study found that participants preferred individualized genetic testing versus race-based medications, but raised concerns about cost, privacy, and discrimination.¹⁴ In the other two, participants were likely to be highly suspicious of the safety and efficacy of race-based drugs.^{13, 15} A phone survey of 1,796 Americans reported that the public was generally supportive and interested in participating in genetics research, including PGx research, but had conflicting views regarding affordability of targeted drugs.¹⁶

Due to the limited understanding of interest in PGx testing among Americans, we conducted an anonymous, random-digit-dial telephone survey of a sample of the U.S. public. This survey ascertained the public’s views about PGx testing (e.g., knowledge of risks and specific uses of PGx tests and how demographics influence their interest in PGx testing). In particular, we examined the public’s interest in PGx testing given three potential risks (DNA sample could be accessed without patient permission, test result could be accessed without patient permission, testing requires a blood draw) and five distinct uses (to predict risk of mild side effects, to predict risk of serious side effects, to understand side effects in self or family members, to select most effective drug to treat illness, or to select appropriate dose or strength) of PGx testing. Past studies have not distinguished between different purposes of PGx testing; we believed it would be informative to learn whether interest varied by the purposes of testing and if such interest was influenced by personal characteristics, familiarity with genetic testing or history of medication side effects as previously demonstrated.¹⁷ Furthermore, we were interested in identifying subpopulations of respondents with lower interest in PGx testing which may warrant further study to understand their concerns, to limit disparities in the use of testing with demonstrated benefits, and maximize benefits of testing. These data can help identify potential challenges of translating PGx testing based on the public’s overall interest as well as interest in specific uses of testing.

Level of interest in PGx testing is comparable to the generally high interest reported for genetic testing for colon cancer⁵ or hereditary cancers in general^{4, 6–8} and heart disease.^{6, 8, 9} There are conflicting data on the relationship between level of education and attitudes toward genetic testing.^{9, 27–30} Some studies have found an inverse relationship between education level and positive attitudes toward genetic testing.^{9, 28} Others have found that individuals knowledgeable about genetic testing have more positive attitudes towards testing²⁹ but also may express skepticism.²⁷ Yet other surveys find no evidence to support a correlation between knowledge about biotechnology in general and attitudes towards it.³¹ Although 20% of respondents in our survey had not heard of genetic testing, we did not observe a relationship between overall interest in PGx testing and awareness. However, we found that those with less than a college degree had a lower interest in PGx testing after being informed of the risks; this association disappeared after they learned about the specific uses of testing. Similar to other studies,³² we found greater awareness of genetic testing in Whites compared to non-Whites, but race was not associated with overall interest in PGx testing.

The order of information presented about genetic testing can affect attitudes toward testing with the information presented first being more influential.²⁴ After assessing overall interest, we did not find presentation of the risks first as most influential, perhaps due to high general interest in genetic testing or familiarity and/or experience with drug side effects or non-response. However, when presented with individual risks such as loss of confidentiality, only a minority indicated they would be interested in PGx testing. Despite the nearly 10-year gap between the two surveys, our findings were comparable to Rothstein & Hornung (2003) with respect to interest in PGx testing given concerns about confidentiality (78% in our survey vs. 70% in their survey would be less likely to undergo PGx testing). As we did not disclose the fact that federal law now prohibits discriminatory actions by health insurers or employers (regulations were still pending at the time the survey was administered), it is not certain whether knowledge of federal protections would have increased interest following presentation of individual risks. Given ongoing concerns, disclosure of these policies should be a required element of the discussion about PGx testing with patients.

As anticipated, presentation of the different uses of PGx testing boosted interest. We had hypothesized that the public would vary in their level of interest of different uses of a PGx test as some uses may be considered more important than others, but found little difference. Commonalities existed between factors predictive of interest in PGx testing given certain risks or intended uses, though no single characteristic was predictive of likelihood, suggesting that a combination of personal factors, awareness of genetics, and health and medication history influence interest in PGx testing. The absence of significant differences could also be attributed to lack of understanding of the different specific test uses (e.g., effectiveness vs. safety). The lack of context or details of a specific treatment scenario may have also resulted in generally high interest in all uses. Four factors were significantly associated with interest in testing for two of the three risks and intended uses presented: awareness of genetic testing, race, education, and personal history of side effects. The lower interest in PGx testing by non-Whites given some risks and intended uses may indicate differences in perceived harms (higher) and value of the information (lower), potentially attributed to mistrust of genetic testing^{33, 34} or the health system in general, but not strong enough to influence overall interest in testing. Interestingly though, race and education were not associated with likelihood of testing given risk of loss of confidentiality as reported by Rothstein & Hornung (2003). Our finding that history of side effects was linked to overall interest confirm previous findings with respect to PGx testing,^{17, 35} analogous to the higher interest in genetic testing in at-risk individuals (i.e., those with a family history).^{36, 37}

Of the minority of respondents that indicated they were initially not very or not at all likely to have a PGx test, about half indicated they would be interested in a non-genetic test that provided similar information about drug response, suggesting that development of non-DNA-based PGx tests may help increase uptake. Interest in a non-genetic test was associated with higher education status, possibly suggesting greater awareness of potential risks of testing. Shields et al.^{38, 39} reported that primary care physicians would be more likely to order a non-genetic test compared to a genetic test to predict response to smoking cessation therapy, suggesting some reluctance, either on the part of physicians or their belief that their patients would be reluctant to consent to a genetic test. Of our respondents who were unlikely to have any testing for drug response, genetic or otherwise, we speculate that other concerns not related to ‘genetic testing’ account for their lack of interest in testing. Given the long-term benefits of PGx testing over a patient’s lifetime, declining testing could have multiple adverse consequences including access to best available therapies if testing is required prior to use. Thus, careful consideration must be given to weighing the benefits and risks of use of a given treatment if testing is not performed, coverage policies of treatments without testing, and alternative approaches to monitoring adverse responses.

Given the sometimes different allele prevalence between populations, it will be essential to include as diverse study populations as possible to ascertain PGx associations as well as potential physiologic functional differences. Groups with lower interest in PGx testing may be less inclined to participate in such studies, creating a significant knowledge gap. On the other hand, groups with higher interest in PGx testing, such as individuals with prior experience of side effects, may be more interested in participating in PGx research. Careful attention should be given to assessing outcomes based on patient self-reporting to minimize confounding.