DTC advertising was associated with an increase in use of HPV DNA tests, but did not promote targeted use of the test in primary screening among age groups of women specified by clinical guidelines. This result is consistent with previous evaluations of DTC advertising, which have found that patients who make a request for advertised COX-2 inhibitors or antidepressants are more likely to receive a prescription than those who do not make a request, regardless of whether the request is in keeping with clinical guidelines [20
The consequences of inappropriate use of advertised health products and services include excess costs, side effects and adverse events resulting from unnecessary use. The desirable balance of appropriate and inappropriate use may vary, according to the costs and benefits associated with each. For example, one study of DTC advertising for antidepressants estimated that while most antidepressant prescriptions driven by DTC advertisements are written for non-depressed patients, the economic costs of treating these patients may be outweighed by the large benefit of treating a small number of depressed patients who would otherwise have gone untreated [22
]. Conversely, treating patients with a newer, more expensive advertised agent that is a substitute for an existing, cheaper alternative may present excess costs that are much greater than the product's marginal benefits in efficacy or acceptability.
To realize the potential of DTC advertising with minimal increases in inappropriate use, approaches that target both patients and physicians may be needed. At present, most DTC television advertisements do not effectively convey that the advertised product is not suitable for everyone, and consumers are unable to answer basic questions about much of the content of DTC television ads [23
]. The appropriateness of patient inquiries may be increased through improved clarity and completeness of advertising; for example, drug facts boxes in advertisements have been shown to increase consumers understanding of prescription drug benefits and side effects [24
Physicians frequently accommodate patient requests for advertised drugs and services, even when fulfilling requests does not result in superior care [25
]. However, our study found that clinical guideline releases were associated with greater increases in appropriate use than in inappropriate use, suggesting that guidelines have the potential to affect clinicians' practices appropriately, even in the context of product marketing.
The impact of guidelines on appropriate use could be optimized at the stages of both guideline development and dissemination. Consideration of expected marketing messages during the guideline development process may help guidelines anticipate the content and prevalence of patient requests. Implementation of proven interventions, such as audit and feedback, reminder systems and academic detailing, upon the release of new clinical guidelines may help to maximize the degree to which advertising-driven patient requests result in appropriate use of new technologies [3
Most evaluations of DTC advertising assess the impact of large-scale nationwide campaigns that begin concurrently with a product's market entry; such studies are limited in their ability to make causal inferences, as pre-campaign usage data is unavailable, and control groups are exposed to at least some DTC advertising. Our study evaluated a DTC campaign that began five years after the initial FDA approval of the advertised product, and that targeted advertisements to local markets over discrete time periods. These unique features allowed us to control for pre-advertising trends, and to evaluate DTC advertising effects by comparing locations exposed to DTC advertisements with comparable unexposed locations.
Our study has several limitations. As in all difference-in-differences analyses, there is a chance that concurrent alternative influences were responsible for the effects we attribute to the interventions; however, the similarity of the increases in HPV DNA test use across two sets of intervention and control groups reduces the likelihood that alternative explanations were responsible for the effects we observe. We are aware of no other relevant events, such as changes in insurance coverage or publication of influential research, that occurred concurrently with the two rounds of the DTC campaign under study. In addition, it is possible that although the DTC and comparison cities had comparable pre-trends in HPV DNA test use, they differed in unmeasured ways that may have influenced adoption of HPV DNA tests.
Our data do not allow us to identify socioeconomic or other characteristics that may influence women's likelihood of being exposed to advertisements, or to determine whether women who received HPV DNA tests saw the advertisements. However, DTC campaigns may influence health care providers or provider groups to change their practice norms, regardless of whether individual patients are exposed to DTC advertisements. Our understanding from a QIAGEN marketing representative is that all DTC cities were targeted with provider-side sales force visits, as well. This limits our ability to disentangle the effects of DTC advertising from the physician promotions reinforcing it. Since virtually all DTC campaigns are complemented by a diverse marketing plan that includes physician detailing and advertisements, we believe that our study represents an accurate picture of the effects of a DTC campaign that includes these supporting elements.
We also did not have any information on the reasons why providers administered seemingly inappropriate HPV DNA tests to women under age 30. Since we used consistent definitions throughout the study period, findings on relative changes in appropriate and inappropriate use should not be biased.
Because market regions may overlap slightly, and because broadcast television stations sell their content for rebroadcast by satellite and cable companies, regionally targeted advertisements may have been viewed in other parts of the country. This may have resulted in a small amount of contamination in our comparison cities, thereby causing us to underestimate the effects of DTC advertising on HPV DNA test use. Therefore, our results may be conservative estimates of the impact of DTC advertising.
Finally, our study of privately insured women cannot provide insight into whether DTC advertising increases utilization among those who need it most. Survey data suggest that those with lower household income and education are less likely to see DTC advertising than those with higher incomes or more education [27
]. Further research is required to explore whether the effects of DTC promotions reach and influence these underserved populations, which are not typically the primary targets of marketing campaigns.
The results of this study suggest that DTC advertising may be an effective way of increasing use of cancer screening or other health care technologies, but that these increases may be composed of some inappropriate use. Importantly, our results also highlight the ability of clinical guidelines to improve the balance of appropriateness by channeling use to target populations. Together, these findings suggest distinct influences of consumer marketing and professional guidelines on use of health care products and services.