Study findings suggest that patients of PA/NPs differ from those seen by doctors with respect to metropolitan residence, insurance type, gender, age, and extroversion scores. With the exception of the extroversion score, these findings are consistent with literature that evaluates factors associated with visits to PA/NPs in outpatient settings.16, 18, 28
However, our study uniquely suggests that perceived health and health care outcomes do not differ except for lower perceived access and lower utilization of some preventive services.
PA/NPs have been utilized to improve access and/or reduce cost while maintaining quality of care. The currently available literature suggests that PA/NPs are improving access by serving underserved populations and treating patients with acute health issues and stable chronic diseases.4, 13, 16, 21, 35
It has been shown that some rural PA/NPs act as a primary provider for a sizable proportion of their patients.19
However, our data suggests that access may not fully explain utilization patterns of PA/NPs as a usual source of care. In addition to non-metropolitan residents and those without insurance or on public programs other than Medicare, women, younger patients, and those with lower extroversion scores were more likely to identify PA/NPs as a usual source of care. In regard to gender, patient satisfaction with same-sex providers may explain this observation.37
Studies suggest a “feminization” of the PA/NP professions2
and that PA/NPs may provide a larger proportion of the woman-provided care in rural areas.3, 4
The younger age of patients of PA/NPs could be interpreted as a possible sign of better health status of these patients compared to those patients who see primary care doctors. However, usual provider type was not associated with measures of health status in our analysis. A more likely explanation may be the lower reimbursement for PA/NPs with Medicare patients.38
Regarding personality, previous research demonstrated that low extroversion scores are associated with receipt of personal continuity of care, reporting of a serious health problem and a willingness to wait in order to see their provider of choice.39
This suggests that PA/NPs may be acting as a usual source of care for a subgroup of patients that considers continuity of care important.25, 39
Utilization of health services and perceived health status of patients identifying PA/NPs and doctors as their primary care provider is similar, but those seeing PA/NPs report lower access scores. Regarding health care utilization, visits to chiropractors were more common in patients of PA/NPs. This could be suggestive of either practitioner willingness to recommend non-drug27
or complimentary/alternative therapies, and/or increased willingness of these patient types to utilize PA/NPs. Also of note, services associated with decreased health status, such as emergency room visits and hospitalizations, showed no significant difference, underscoring the finding that there is no significant difference in patient health status by provider type. Patients of PA/NPs were less likely to utilize some preventive services such as complete health exams and mammograms. This result is contrary to literature reporting that PA/NPs do as well or better than doctors in meeting recommended preventive health interventions.18, 22, 35
Metropolitan designation is determined at the county level; therefore, it is possible that we could not completely control for differences between doctor and PA/NPs practice location characteristics. PA/NPs are more likely to practice in rural areas; therefore, lower levels of some preventive services may be related to broader access issues for underserved populations.
The average GHAA access score for patients of PA/NPs was approximately 0.2 lower than that of patients of primary care doctors. When considered with the other access variable, which suggests that patients of PA/NPs do not perceive any difficulty or delays receiving care, PA/NPs’ availability may not entirely explain the effect. One explanation could relate to public perception. Some proportion of participants that use PA/NPs may not perceive difficulties or delays, but would prefer to see a doctor, rather than an “assistant.”
There are several limitations to the study. First, the data source is a longitudinal cohort study of a population homogeneous in race and age as well as educated and insured. While potential confounding is minimized, the results may not easily be generalized to other populations. Second, provider utilization and outcomes are evaluated simultaneously due to unavailability of provider data in sequential surveys. Third, verification of reported provider type is lacking. Patients may misclassify the provider type of their usual source of care. Since the average reported length of relationship with a usual provider for the WLS participants identified for this study was approximately nine years, we anticipate that this misclassification, as well as misclassification of all advanced practice nurses as an NP, is minimal. However, if present, misclassification would more frequently result in PA/NPs misclassified as doctors than doctors as PA/NPs. Since the proportion of patients that identify PA/NPs as a usual provider is relatively small (2.57% in U.S., 4.51% in WLS),40
we estimate that this would have a negligible effect on findings. Fourth, interpretation of certain variables has limitations. The metropolitan variable is a county-level definition, suggesting a homogeneity of population that may not exist, potentially diluting the reported effect of geography. The survey question identifying provider type asks about a “usual” source of care. No quantification is provided; therefore, it is unknown if this represents true autonomous care provided by PA/NPs. Finally, the number of respondents identifying PA/NPs as their usual source of care is relatively small.
Multiple strengths of the study are also noted. The study population represents a demographic that is recognized for its utilization of PA/NPs35
in a state with a significant proportion of its population in all three geographic categories. It is also an age cohort that precedes the bulk of the baby boom generation by approximately 10 years, potentially providing early indications of utilization trends for a growing sector of the US population. Utilizing state-level data provides additional advantages. The richness of the data allows for a comprehensive analysis of factors predicting utilization that is rarely found in national data sources. Finally, Wisconsin has a regulatory environment allowing for a broad scope of practice and greater utilization of PA/NPs.21
The results of this study are not only useful for Wisconsin State policy, but may inform other states looking to expand the utilization of PA/NPs.
In a policy era that is focused on reducing costs while increasing access and quality, increased utilization of PA/NPs is frequently offered as one solution. The results of this study suggest that while the population served by PA/NPs is unique, patient factors related to need for health care are not significantly different and perceived access to care is lower despite relatively few differences in utilization of services. When taken in context with the current body of literature, the data suggest PA/NPs may be acting in a substitute role as primary care providers to underserved patients with a range of disease severity. While this new evidence should be considered in policy deliberations on clinician work force and reimbursement, caution must be exercised. Currently, clear operational definitions for the potential roles of PA/NPs is lacking, as is evidence of the potential of PA/NPs to contribute to the functions of primary care within each of the potential roles.17
Until these questions are answered, efficient utilization of PA/NPs will remain elusive.