We found evidence associating the ALLHAT/JNC7 Dissemination Project with increased use of thiazide-type diuretics in the U.S. Although we had hypothesized a graded relationship between intervention intensity and thiazide-type diuretic use, this pattern was evident only in the NDTI physician survey data. Nonetheless, both data sources indicate that diuretic prescribing increased nationally and that counties not receiving the intervention had slower growth in diuretic use when patterns before and after the time frame of the intervention are compared. We acknowledge that this is an ecological association and that counties selected for dissemination efforts may have differed from other counties.
The magnitude of change associated with the intervention is small, likely corresponding to the limited dose of the intervention. The observed pattern of change in thiazide-type diuretic prescribing also differs somewhat between the survey information on prescribing (NDTI) and pharmacy dispensing information (Xponent).
The intervention focused on persuasive communication about prescribing behavior presented by community colleagues, as distinct from an emphasis on clinician knowledge. This strategy used methods known to be effective in academic detailing, including role modeling by peers, visits to individuals or practice groups and careful delineation of the target behavior (19
). While designed to be more intensive than continuing medical education, the intervention did not include individualized efforts to change prescribing, such as performance standards, behavioral feedback strategies, or practice-based redesign. Greater intensity and individualization might have had greater impact, but would have compromised the national reach of the Dissemination Project. Nonetheless, our findings are consistent with past studies of academic detailing and show its potential to motivate changes in physician practices.
Other issues may have blunted the ability of the ALLHAT/JNC7 Dissemination Project to convince community physicians of the relevance of ALLHAT’s population and methods, and the applicability of the trial’s findings. The intervention began nearly two years after the publication of the ALLHAT summary results and there was limited opportunity to generate media coverage that might have synergistically magnified the effect of the intervention. During the time period of the intervention, several other clinical trials were published that were promoted as casting doubt on the role of thiazide-type diuretics (25
). This may have complicated the messages delivered by the intervention and reduced the likelihood of prescribing changes. Similarly, there was substantial questioning of the ALLHAT findings by recognized hypertension authorities, as well as by the pharmaceutical industry, that likely reduced the potential impact of the results on clinical practice (27
). For example, unwarranted concerns regarding the use of thiazide-type diuretics in patients with diabetes may have hampered efforts to alter prescribing practices (28
). ALLHAT leaders, however, have published multiple commentaries in high-prestige journals that enumerate counterarguments to such criticisms (29
While the ALLHAT/JNC7 Dissemination Project may have increased the use of thiazide-type diuretics, other changes in prescribing practices are less consistent with evidence. In particular, the continued increase in the use of ARBs and the decrease in ACE inhibitors and calcium channel blockers represent trends that are not congruent with the accumulated evidence on outcomes. These changes add substantially to the cost of hypertension treatment, especially given the recent availability of multiple generic ACE inhibitors and calcium channel blockers.
The findings of this study should be interpreted cautiously in the context of the following limitations. This was an ecological analysis conducted at the level of U.S. counties and any association does not necessarily imply a causal relationship between the Dissemination Project and changing patterns of thiazide-type diuretic use. Furthermore, the sites selected for Investigator-educator activities were not selected randomly and may differ from those in other geographic areas. Despite this potential, the non-random allocation of counties to differing intensity levels of the intervention is unlikely to explain our results. Investigator-educators were selected based on their interest and neither these physicians nor project staff were aware of baseline patterns of thiazide-type diuretic use. Specific efforts were made to select a geographically diverse panel of investigator-educators.
Use of the population aged 50+ years in the Xponent analysis provides an inexact proxy for the population with hypertension. There also may be substantial variation induced by other geographically-varying factors (e.g., drug promotion of non-thiazides), as well as variation connected with the measurement of prescribing patterns. This variation may have made it difficult to detect a more sizable effect of the Dissemination Project and may account, in part, for the differences in findings between the two data sources.
NDTI and Xponent are different data sources and represent distinct populations that might differ in their response to the intervention. NDTI data on office visits by patients with hypertension will over-represent patients making frequent doctor’s visits, including those requiring changes in their medications. Xponent, representing pharmacy data on new and refilled antihypertensive medications, will include patients treated with these drugs for reasons other than hypertension. To a greater extent than NDTI, Xponent will reflect patterns of refilling and discontinuation influenced by factors beyond physicians’ control. These two sources of information also differ in the metric of measuring diuretic use and potential biases. Dissemination efforts were coded by physician office location in NDTI and pharmacy location in Xponent. With their advantages and disadvantages, the use of NDTI and Xponent together provides some degree of cross-validation given their largely concordant results.
Although other explanations cannot be excluded, there was a statistically significant increase in thiazide-type diuretic prescribing that was geographically associated with clinical investigator centered academic detailing aimed at increasing use of thiazide-type diuretics. These dissemination efforts focused on the implementation of guidelines derived from the ALLHAT findings, but also emphasized the role of thiazide-type diuretics in patients requiring multiple medications. Corresponding to the minimal intervention dose, the effect of the ALLHAT/JNC7 Dissemination Project is small. In addition, other factors, including controversy regarding the appropriate role of thiazide-type diuretics, may have blunted the intervention’s impact. Academic detailing has the potential to improve prescribing patterns, but may require greater intensity to facilitate translation of clinical trials evidence into community practice.