This study focused on the use of imaging for uncomplicated acute low back pain because it is prevalent and well established guidelines indicate that rapid or advanced imaging is not beneficial in the absence of specific complicating features or comorbid conditions.5,6,7
We found that rapidity and modality of imaging for back pain was associated with non-clinical characteristics of patients and the physicians and practices that treated them. Low-income and minority patients, and those treated in smaller practices or practices more reliant on Medicaid revenues received less rapid and advanced imaging than higher-income or white patients, and those in larger practices or settings less reliant on Medicaid. These results are consistent with previously reported patterns of care in terms of groups who tend to receive fewer services, although here, the patterns represent better quality care in contrast to when measuring quality in terms of underuse.19,20
Our findings were consistent across the timing or number of imaging studies, and for all modalities. Moreover, patients cared for by physicians exposed to incentives based on patient satisfaction received more rapid and advanced imaging, Conversely, those whose physicians were exposed to both clinical quality and productivity incentives received less rapid and advanced imaging.
The association between exposure to satisfaction incentives and the level of imaging is not unexpected. Patients may consider imaging reassuring, and those with higher socio-economic status may be more successful in obtaining testing in this context. But in contrast to generally underused services such as diabetic monitoring, more rapid or advanced imaging for LBP may not benefit patients, and may result in harm.22,23
Contrary to our hypothesis that incentives focused on underuse might result in greater potential overuse, we observed an inverse association between exposure to clinical quality incentives and the level of imaging. These results should be interpreted with caution as we had only a small number of observations for some combinations of incentives. Nevertheless, they suggest that quality-based incentives may improve appropriateness of care in some unmeasured arenas. This could reflect a broad ecologic effect, if physicians exposed to existing incentives become more generally aware of, and adherent to, clinical practice guidelines.24
Alternatively, physicians exposed to quality measurement may be less vulnerable to the effects of incentives that encourage imaging.
We also found that exposure to both clinical quality and satisfaction incentives among a small fraction of PCPs resulted in less rapid or advanced imaging than with either incentive alone or no incentives at all. Although some prior studies suggest that patient satisfaction tends to correlate with clinical quality,25,26
Landon et al. compared the experiences of Medicare beneficiaries in the fee-for-service vs. managed care programs, and found instead that the two systems had different strengths in quality versus satisfaction performance.27
Our findings are also consistent with those of Weyer et al., who reported that improvements in preventive services were associated with declines in patient satisfaction.28
Although our results require confirmation in larger populations of physicians facing this relatively rare combination of incentives, it is possible that physicians less pressured to maximize visit volume can better align their efforts to perform well on both clinical quality and patient satisfaction (e.g., by spending more time providing reassurance about deferred imaging). However, these benefits would accrue to relatively few patients, as far more physicians face productivity incentives than other types of incentives.29
We found that one-third of imaging studies were performed within the PCP’s practice organization, and that patients treated in large group practices were modestly more likely to receive rapid and advanced imaging than those treated in smaller practices. As large groups are more likely to have the resources to invest in imaging equipment,30
our results are consistent with other studies suggesting that practice-owned equipment results in supplier-induced demand and physician self-referral.31
These associations were independent of the higher likelihood that physicians in large practices were exposed to performance incentives. They contrast with studies showing that larger practices tend to outperform smaller ones in quality improvement efforts and on standardized measures emphasizing underuse.19,32,33
Finally, we found that many patients received imaging on the day of diagnosis. These care patterns are inconsistent with guidelines that recommend a trial of conservative therapy first, and suggest opportunities for quality improvement.
Our results should be interpreted within the context of our analytic approach. We could not determine appropriateness of imaging for a given patient. Ours is a comparative analysis of the level of imaging relative to patient, physician, and practice characteristics, and not an attempt to benchmark the behavior of individual physicians. The inability to identify particular cases of overuse with certainty does not invalidate our findings because all physicians are subject to such errors in coding and ascertainment. As an example, for our results to be biased, physicians would have to be more likely to code diagnoses of “red flag” conditions for minority patients than for white patients, at the same time that they are less likely to order imaging studies for minority patients. Although rates of back pain complications and hospitalizations was higher for patients receiving more rapid or advanced imaging, these differences may reflect, in part, events triggered by the initial imaging study itself and/or the relative aggressiveness of care delivered by physicians who are more likely to order imaging. Rates of cancer diagnoses were no higher for patients who had more rapid or advanced imaging.
We cannot be certain that each CTS PCP was truly responsible for imaging decisions for the patients studied, because claims-based attribution may not reflect actual care relationships.33
However, our conclusions were robust under both more liberal and more restrictive attribution approaches, and when we focused on patients whose initial LBP diagnosis was coded by the PCP, or those who saw only that physician between the dates of diagnosis and imaging. Thus regardless of the involvement of other providers, the level of imaging appears to be related to the characteristics of a patient’s PCP.
Our findings require confirmation with a broader set of overuse measures, but nevertheless have important implications. Development of more overuse metrics would balance out current measures that are heavily weighted toward underuse, perhaps by leveraging research on the comparative effectiveness of different treatment options.34
It is not surprising that physicians and practices with attributes associated with underuse of care are less likely to overuse imaging. However, our results may provide a rationale for tailoring packages of performance metrics to practice attributes. For example, a practice with high Medicaid revenue, many minority patients and minimal physician incentives for maximizing patient satisfaction may be more likely to benefit from measures emphasizing underuse. In contrast, practices with less Medicaid revenue, fewer minority patients and more satisfaction-based incentives may be more likely to benefit from performance measures that include overuse.
More balanced measurement of overuse and underuse might also allow insurers to design incentives to counter both. For example, insurers could offer higher co-payments for services that tend to be overused but lower or no co-payments for generally underused services. Similarly, bonuses could encourage physicians to avoid overused services or increase underused services. Mandatory delays in ordering overused services in the absence of clinical “red flags” is another alternative tool. Such interventions would need to avoid limiting necessary care particularly for low-income patients, but in the context of fee-for-service reimbursement, targeted and balanced incentives could better align the dual goals of quality improvement and cost containment.
Patterns of care revealed by the application of a single measure of potential overuse point to different foci for performance improvement than when measurement focuses on underuse. Given possible reversal in direction from the typical “quality advantage” for important subpopulations of patients and physicians, measuring overuse alongside underuse may be critical for improving the overall appropriateness of care.