In a nationwide cohort of elderly patients with AMI, our study found that physicians who were board-certified in family practice, internal medicine, or cardiology were modestly more likely than nonboard-certified physicians to prescribe aspirin and β-blockers. The higher use of aspirin or β-blockers persisted in multivariate analysis for board-certified Internists and cardiologists. These findings suggest that board-certified physicians provided slightly higher quality of care as assessed by these guideline-recommended treatments for AMI.
The reasons for why board-certified physicians treated a higher proportion of patients with guideline-recommended therapies are unknown but likely multi-factorial. Cabana et al.25
have identified several mechanisms thought to affect physician adherence to clinical guidelines: knowledge, attitudes, and external barriers. For example board-certified physicians may be more aware of or more familiar with practice guideline recommendations as, on average, they complete more hours of continuing medical education and report more time reading journals.26
With respect to attitudes, it is possible that board-certified physicians may agree with clinical guidelines more often than nonboard-certified physicians, leading to higher treatment adherence. Whether differences in attitudes exist is unclear, but some studies correlate board certification examination scores with higher subjective ratings of clinical practices during and after residency, suggesting that board-certified physicians adhere more consistently with consensus-defined practices.27–29
Lastly, board certification may serve as a marker for hospital environments that support the use of clinical guidelines and reduce barriers to their use.
Why was board certification only associated with modest differences in aspirin and β-blocker use? One possibility may be that the board certification exam may be a sensitive assessment of a physician's knowledge base, but less effective for identifying behavioral qualities such as ability to translate evidence from clinical trials into practice, or comfort level or attitudes toward rapidly initiating therapies based on clinical guidelines. Because differences between board-certified and non-board-certified physicians were modest, and even board-certified physicians had room for quality improvement, caution should be exercised when attempting to use board certification as a marker of quality—treatment by a board-certified physician does not necessarily imply optimal adherence to guideline-recommended therapies.
Given the differences in aspirin and β-blocker use, it seems paradoxical that board certification was not associated with improved survival after AMI. One explanation is that the absolute survival benefit was too small for our analysis to detect. Assuming that untreated 30-day mortality was 25% and that aspirin and β-blockers each independently reduce mortality by a relative 25%,30,31
and that there was an absolute 5% difference in the use of these therapies between board-certified and nonboard-certified physicians, this would imply an ~0.5% absolute mortality difference. Finding a statistically significant difference in mortality of this magnitude is difficult; for example, a clinical trial would require over 180,000 patients to detect a mortality difference of 18.0% and 18.5% at 80% power with an α of 0.05.
Our study adds to the existing literature by demonstrating a modest correlation between board certification and quality for the treatment of a life-threatening illness in an acute care hospital setting. Previous studies that examined clinical guideline-based measures of quality were limited to examining care in the ambulatory setting for preventative care activities11
or for screening mammography.12
One study on board certification and AMI by Norcini et al.32
examined mortality, but not quality-of-care measures. This study found that care by a board-certified physician was associated with a 15% lower in-hospital mortality after hospitalization for AMI.32
However, the explanation for the dissimilar results may be that the Norcini study examined AMI hospitalizations in a single state, and used different clinical risk-adjustment methods.
The absolute differences in these quality measures between board-certified and non-board-certified physicians are probably smaller today as their use has increased over time, in particular, for β-blockers.33
However, even the existence of a difference between board-certified and non-board-certified physicians in 1993 to 1994 is an important finding, given that major clinical trials that proved the efficacy of aspirin and β-blockers after AMI were published at least 5 to 10 years before the study period,30,31
and suggests the potential for analogous differences from newer therapies in current clinical practice.
Our study has some limitations. Board certification status depended on accurate reporting in the AMA Physician Masterfile; however, misclassification of board certification status would make the physician groups appear more similar, biasing results toward the null and underestimating the relationship between certification and outcomes. We could not differentiate between nonboard-certified physicians who failed the board examination (a true board certification attributable difference) and nonboard-certified physicians who did not attempt certification (a difference attributable to physician self-selection). However, distinguishing reasons for lack of board certification is arguably a moot issue for patients or health care organizations. Board certification may also be associated with differences in documentation of contraindications or comorbidities. Although we considered characteristics of the attending physician, we were unable to determine whether this physician was solely responsible for the majority of decisions made during the patient's hospitalization, or whether care was directed by subspecialty consultants.
Although we found that board certification, on average, was modestly correlated with several guideline recommended treatments for AMI, our study illustrates the challenges of using board certification as a marker of quality. Board certification was not a strong measure of quality, as treatment by a board-certified physician did not guarantee use of aspirin or β-blockers in all patients for whom treatment was indicated. Indeed, for each of the quality indicators, the differences between the use of guideline recommended treatments by board-certified physicians and maximal adherence were larger than the difference between board-certified and nonboard-certified physicians. Although there is a correlation with markers of higher quality AMI care overall, even board-certified physicians have considerable room for improvement.