Nurse practitioners (NPs) and physician assistants (PAs) often practice independently and can prescribe medications in most states
(1). Their numbers have dramatically increased in recent years
(1, 2), and understanding how they perform is an important health policy issue. This question may be particularly important in rural and inner city areas with physician shortages and in countries with limited health care resources
(3). Studies have suggested that both the quality
(4-6) and the cost-effectiveness
(7) of primary care provided by NPs are similar to that provided by physicians. These findings, however, may not be generalizable to other settings and, in particular, to specialty care
(8, 9).
Discussion
In our national study of patients who were cared for in CARE Act Title III HIV clinics, 20% of patients received most HIV care from NPs and PAs. The performance of NPs and PAs in caring for patients with HIV was similar to that of physicians trained in infectious diseases and general medicine HIV experts for 6 of the 8 quality measures that we examined and was superior to that of HIV expert physicians for the other 2 quality measures. Nurse practitioners and PAs performed statistically significantly better than generalist non–HIV experts on 6 of the 8 quality measures. Performance rates substantially differed from a clinical standpoint, from 7 to 19 percentage points.
One possible explanation for our findings is selection bias. Patients cared for by physicians may have had more complications than patients cared for by NPs and PAs. Our data do not suggest this. Although patients cared for by NPs and PAs were slightly younger, were more likely to be women, and had slightly fewer comorbid conditions, they were also more likely to have drug abuse problems, and we adjusted for these and other patient characteristics in the multivariable model. Other unmeasured patient characteristics may relate to both selection into an NP and PA practice and the quality measures that we assessed. However, the consistency of the effects that we observed across measures of treatment, prophylaxis, prevention, and access supports the validity of our findings.
A second possibility is that NPs and PAs practiced at sites that were better organized for the care of patients with HIV. Our analyses of site characteristics, however, revealed only 1 statistically significant difference—more sites at which NPs and PAs were primary HIV care providers had substance abuse counselors. These sites had slightly fewer full-time–equivalent physicians, but this should have made it more difficult for NPs and PAs to perform well. When we controlled for these site-level factors, the findings did not change.
A third possibility is that NPs' and PAs' practices were less busy and were more focused on HIV care, allowing them to focus on the processes that we assessed. Nurse practitioners and PAs did see fewer outpatients per week than physicians and a higher percentage of patients with HIV. However, when we adjusted for these factors in multivariable models, our findings did not change, suggesting no confounding by site.
Our previous work showed that HIV expertise is strongly associated with higher-quality care for both physicians
(12, 17) and HIV care sites
(19). The NPs and PAs we studied were experienced HIV care providers, following an average of 108 patients with HIV, and most of their patients had HIV. In addition, they typically practiced in environments with several supports for HIV care, including HIV care teams and access to expert HIV physicians. Furthermore, more than 46% of patients cared for primarily by NPs and PAs also saw a physician during the year we studied. These data suggest that key elements in the performance of these NPs and PAs may be high levels of experience, focus on a single condition, and either participation in HIV care teams or other easy access to physicians with HIV expertise. Nurse practitioner or PA performance may also have been higher because these clinicians saw fewer patients per week than physicians.
Our data show that under certain conditions, NPs and PAs can function as lead HIV clinicians and can provide care that is similar to, and for some measures better than, that provided by physicians. Between 1992 and 2000, the number of NPs, PAs, and certified nurse midwives has increased by 160%
(2). National data show that patients are seeing nonphysician providers in addition to, and not instead of, physicians
(20, 21), and our study suggests that this is also true for patients who see NPs and PAs for their HIV care.
Our findings may be important for HIV care sites located in rural, underserved, or resource-constrained care settings. In care settings where access to physician providers is limited, properly trained and supported NPs and PAs may help address this access problem. We should note, however, that HIV expert physician backup is almost certainly necessary for NPs and PAs to provide high-quality HIV care. Whether NPs and PAs are more cost-effective than physicians is unclear. Although NPs and PAs usually earn less than physicians
(22), some data suggest that they have longer visits
(6, 7) and order more tests
(6). Many countries with limited resources are scaling up the delivery of antiretroviral medications
(23-29), and our data suggest that properly trained and supported nonphysician health professionals can play a useful role in these settings.
We examined quality measures that could be assessed by a medical record review. All but 1 (nondetectable viral load) of these measures are process measures. Our findings may have differed if we could have assessed mortality rates, hospitalization rates, appropriate management of opportunistic infections, changes in health status, medication adherence, or patient reports about or ratings of care
(30). Similarly, our findings might have differed if we had measured the performance of more complex HIV-related care decisions (such as managing treatment failure) or had assessed other types of quality in these patients (such as appropriate care of depression, diabetes, hypertension, or hyperlipidemia). Four care processes that we assessed (purified protein derivative testing, hepatitis C screening, Pap smears, and influenza vaccinations) are simple for anyone with basic clinical training to implement, and the remaining 4 care processes (HAART, viral load control,
P. carinii prophylaxis, and visit frequency) are the subject of detailed clinical practice guidelines
(31, 32). Nonetheless, we found similar results across all 8 quality measures. Finally, we studied patients receiving care in clinics that have CARE Act Title III funding, and we cannot know whether our findings are generalizable to other settings. Sites that receive this funding, however, disproportionately care for patients with low incomes and complex social problems. We therefore expect that NPs and PAs would have less, not more, difficulty caring for more advantaged populations.
The preconditions for the NP or PA performance observed in our study are high levels of experience, focus on a single condition, and either participation in teams or other easy access to physicians and other providers with HIV expertise. These results may be particularly salient for care settings in which access to physician HIV experts is limited, including countries with limited resources for health care.
Quality of HIV Care Provided by Nurse Practitioners, Physician Assistants, and Physicians.
Wilson and colleagues did not make any distinction between nurse practitioners and physician assistants in their report (1) about the quality of HIV care provided by nurse practitioners, physician assistants and physicians. Both groups can have different backgrounds, training experiences and emphasis on practice style that can confound the results of their study. The authors also did not precisely define "˜expertise' in the field of HIV treatment among various physicians. The answers to the questions posed by the authors may simply indicate the physicians' level of confidence rather than true competency.
1. Wilson IB, Landon BE, Hirschhorn LR, et al. Quality of HIV Care Provided by Nurse Practitioners, Physician Assistants, and Physicians. Ann Intern Med. 2005;143:729-736.
Conflict of Interest:
None declared