Our results suggest that overprescribing of lipid lowering agents may be significant in magnitude and increasing. At baseline, overprescribing of lipid lowering medications was primarily associated with physician and practice characteristics such as board certification, specialty, and practice setting. Longitudinal increases in overprescribing were also primarily related to physician and practice characteristics. Organisational incentives had little association with overprescribing, consistent with literature suggesting that most managed care strategies to influence physician prescribing have limited effectiveness.23
Our results are consistent with research demonstrating that guidelines may not be applied in clinical practice.12,13,24,25,26
Despite substantial efforts to promote NCEP guidelines and to intensively fund physician education efforts, only 59% of internists in an American College of Physicians survey were familiar with NCEP guidelines.24
Further, in a study about family physicians' awareness of hyperlipidemia consensus statements, less than 20% of respondents knew the exact values recommended in the statements.25
Although interventions to change physician prescribing27
and improve guideline adherence12,13
have been studied extensively, few studies have examined factors associated with increasing overprescribing when guidelines are implemented in actual practice. Recognition of factors associated with increased overprescribing after guideline publication may inform future guideline implementations and interventions to decrease overprescribing.
No non‐interventional studies have examined physician and practice characteristics associated with longitudinal increases in overprescribing. However, a randomised trial of an educational intervention suggested that prescribing changes were independent of physician characteristics, including age, board certification, specialty, rural versus urban practice, intensity of previous target drug use, and size of Medicaid practice.28
This contrasts with our results that international medical graduates and physicians with more hours in direct patient care had larger increases in overprescribing. This may illustrate the distinction between randomised trials of interventions that target specific improvements in physician behaviour and changes in actual clinical practice after guideline publication. Many factors may affect these “real world” behaviour changes, but the relationship between overprescribing and more hours in direct patient care may be partially due to lack of agreement with guidelines. In a survey of internists who were members of the American College of Physicians, physicians seeing patients more than 20 hours per week were more likely to feel that guidelines challenged physician autonomy and were too rigid for actual use with individual patients than those with less clinical time.24
Alternatively, this finding may represent the struggles that busy clinicians face in becoming aware of or familiar with guidelines. Lastly, international medical graduates may receive perplexing messages about hyperlipidemia management as guidelines and units of measure for lipid levels vary nationally. However, a previous study showed that, although national guidelines varied, the NCEP guidelines would treat more patients than several other international guidelines.29
Thus, this would not explain the association between international medical graduates and increasing overprescribing. In addition, the definition of oral agent was left to the respondent. If international medical graduates were more likely to recommend dietary supplements, this might explain the association between overprescribing and international medical graduate status.
In contrast to studies of change over time, previous literature has suggested that a number of physician and practice characteristics are associated with baseline inappropriate prescribing. These physician characteristics include older age,30,31
family/general practitioner compared with other specialties,30,32
lacking specialty certification,31
and practice outside an urban area.30,32
These findings are consistent with our results that physicians who were not board certified, were in solo or two‐physician practices, or were family physicians were more likely to prescribe inappropriately. In addition, physicians who had more practice revenue from either Medicare or Medicaid were more likely to prescribe inappropriately at baseline, perhaps reflecting awareness of their patients' reduced financial barriers to prescription drug use.
As in all observational studies, unmeasured factors may contribute to or explain the relationships observed. While CTS data on physician, practice, and organisational characteristics do allow adjustment for many potential confounders, the impact of prescription drug insurance or formularies could not be assessed. It is conceivable that responses to the vignette may not reflect actual practice, although previous literature has shown that vignettes accurately reflect practice behaviour.33
Overprescribing of lipid lowering agents was examined with a single clinical vignette, so the study results may not be generalisable to practice overall. In addition, the 2 year interval between surveys may not be sufficient to create a detectable impact of some organisational incentives.
Although the guidelines were unchanged during the study period, publications about the benefits of stricter LDL control34,35
may have led some physicians to prescribe beyond guideline recommendations. Also, while the vignette states the patient has “no other cardiac risk factors”, physicians may have believed there were some patients similar to the vignette patient for whom treatment could be indicated based on factors not explicitly stated in the vignette. To address these possibilities, we performed a sensitivity analysis with less stringent cutpoints for appropriate prescribing. The less stringent cutpoints allowed physicians who prescribed for 5–10% of such patients to be considered as appropriate prescribers. Analyses based on these less stringent cutpoints did not alter the conclusions of the study.
The marked increase in overprescribing of lipid lowering agents may result from a number of factors directed to either patients or physicians. These include direct to consumer advertising (DTCA) or physician directed advertising by pharmaceutical companies, both of which have been shown to increase physician prescribing.15
DTCA is a particularly likely cause as guidance by the Food and Drug Administration in 1997 (between the two rounds of the CTS) facilitated DTCA. Both hyperlipidemia diagnoses and the number of lipid lowering agent prescriptions are positively associated with DTCA expenditures for lipid lowering agents.14
Marketing strategies directed towards physicians have also been shown to affect prescribing,36
despite the fact that many of the promotional statements in advertisements for lipid lowering drugs are not supported by the cited reference.37
Additionally, efforts to raise awareness of cardiovascular health38
and the use of cholesterol screening as a marker for quality of care39,40
could contribute to our findings. Although these factors cannot be assessed with our data, they could be considered in future research on overprescribing of lipid lowering agents.
This work shows the magnitude and trend of overprescribing of lipid lowering agents during a period of stability in the NCEP guidelines while also examining factors associated with this overprescribing. Recognition of overprescribing of lipid lowering agents is critical in the context of concerns about their safety.8,9,10
Furthermore, previous work has shown our inability as a nation to fund lipid lowering agents for all patients who meet treatment criteria.2
The findings of our study indicate that we are even less well situated to meet the treatment needs of our patients. This is particularly relevant given recent policy changes surrounding prescription drug coverage,7
and NCEP guideline updates focused on tightening lipid level goals and thus increasing the number of people for whom such drugs are recommended.3,5
This work also suggests that interventions to curb overprescribing should consider the role of physician and practice characteristics in shaping physician behaviour. Because data on whether a physician prescribes inappropriately are rarely available, identifying these physicians through their common characteristics may promote effective targeting of quality improvement efforts. Furthermore, the characteristics of these physicians suggest that education (lack of board certification or international medical graduates), lack of time for educational pursuits (in solo or two‐physician practices), and financial incentives (those with more practice revenue from Medicare or Medicaid) are potential root causes for overprescribing of lipid lowering agents.