One year after the introduction of the first protease inhibitor, 30% to 40% of eligible patients with HIV infection were taking HAART therapy. This number had risen to 60% to 70% just 6 months later. In this study, specialty training and expertise of the physicians caring for these patients were important predictors of early adoption and use of HAART. At both 1 year and 11
years after the approval of the first protease inhibitor, we found that patients of non-expert generalist physicians had lower rates of HAART therapy than either patients of physicians with specialty training in ID or patients of generalists physicians with expertise in the care of HIV patients. These findings, however, were attenuated by June 1997 and no longer statistically significant, suggesting that over time, HAART therapy was successfully adopted by the broader physician community such that generalist physicians who lacked expertise in HIV care were also using this important therapy. These findings are consistent with the literature on the diffusion of innovation.25
This is the first study that we are aware of to simultaneously examine the influence of formal training and expertise (including caseload) on the treatment patterns of a nationally representative population of patients with a chronic medical condition. These findings suggest that generalist physicians with appropriate experience have the potential to provide high-quality care to patients with complex chronic illnesses, at least as measured by the specific measure of technical quality that we examined in this study, and that their patients get similar access to important new therapeutic advances. Conversely, physicians with little experience should not be relied upon as the primary caregivers for complex conditions unless they are able to co-manage the patients with an expert provider. Consequently, guidelines and treatment algorithms should be designed to incorporate the possibility of differential levels of expertise among generalists (and specialists) and should acknowledge that generalist physicians are often able to provide high-quality care as well. While guidelines for the treatment of HIV infection have evolved over the last several years, we examined measures of HAART use that were thought to be state of the art during the time period of our study. Thus, these changes in recommendations would not affect our main conclusions with respect to physician specialization and the adoption and use of state-of-the-art treatments for a complex chronic medical condition.
In research conducted before the introduction of protease inhibitors, Kitahata et al. found that patients of physicians who had treated at least 5 HIV-infected patients had lower mortality.9
Findings from Stone et al., who also used a cutoff of 5 patients to define low-volume physicians, also indicated that experience in HIV care was beneficial, but other cutoffs were not reported.10
In our study, few physicians were caring for 5 or fewer patients. Our data suggest that as the AIDS epidemic has matured, physicians who care for HIV-infected patients tend to have a higher caseload. Thus, as the complexity of care has increased, HIV caseloads have increased, suggesting that physicians require a higher threshold of patients to maintain competence. Despite this, low-volume physicians continue to care for almost 10% of the population with HIV infection.
Some have hypothesized that patients who want to pursue the most advanced and aggressive therapy will preferentially seek out physicians trained in infectious diseases and/or the most-experienced clinicians. While patients of ID physicians did have slightly more advanced HIV disease, the vast majority of patients seen by each class of physicians rated taking antiretroviral therapy as “definitely or probably worth it.” Nonetheless, fewer patients of generalist non-experts agreed with this statement, so patient attitudes were adjusted for in our multivariable analyses. Thus, while patient attitudes toward taking ARVs were important predictors of being on HAART therapy, differing attitudes did not account for differences in use of HAART therapy across types of physicians.
Studies of other conditions have shown that specialists are usually more knowledgeable than generalists about diagnostic techniques26,27
and efficacious therapies.28,29
In addition, specialists tended to provide care deemed appropriate at higher rates than generalists when processes of care are examined (using chart reviews or patients' reports) for acute myocardial infarction ,30,31
, multiple sclerosis,36
In addition, studies have demonstrated that high-volume physicians have better outcomes for treatment processes such as angioplasty and many surgical procedures.38–41
Our findings extend these studies by examining formal training and caseload simultaneously and suggest that caseload, as a measure of expertise, might be as important or more important than specialty training. In addition, we also show that while specialized physicians adopt new treatment strategies more rapidly, these innovations successfully diffuse to the broader physician community over time. To the extent that a particular disease condition is experiencing rapid introduction of new treatment modalities, however, expert clinicians (whether by virtue of specialty training or other modes of developing expertise) will generally provide more-current therapy to patients.
Our study has several limitations. First, although we were able to identify appropriate links to physicians for over 70% of the sample, there might have been unmeasured differences between linked and unlinked patients. Including patient characteristics and weights adjusting for nonresponse in our models, however, largely controlled for these potential biases. Furthermore, propensity score analysis results were consistent with our original findings. Second, while we carefully identified the physicians caring for the HCSUS patients, some patients may have switched physicians at some point in time. Consequently, we focused our analysis on the time period closest to the identification of the physicians. In addition, we would expect that any misclassifications would make it more difficult to detect true differences. Third, while this is among the largest studies to date of this type, small differences can sometimes have a larger cumulative impact when they apply to large numbers of patients. Thus, we might have lacked power to detect important differences between ID physicians and general medicine experts. Finally, we only examined 1 important aspect of care for patients with HIV infection. We might have observed different results if we had examined other processes of care, such as the appropriate treatment of opportunistic infections.
Our findings demonstrate that expert generalists, whether by virtue of experience or interest, are able to provide care of quality equal to that of specialists, at least as measured by the use of HAART therapy. Guidelines and strategies to improve care for HIV patients should therefore promote the use of expert generalists as well as ID physicians. In addition, physicians without such expertise care for a small but substantial proportion of patients. Developing strategies to obtain appropriate expert input for these patients might also lead to improved outcomes.