Saturday, 16 November 2019: 3:15 PM
Access to care for Medicaid beneficiaries lags behind individuals covered by Medicare and private insurance (Hing, Decker, & Jamoom, 2015; Polsky et al., 2017). This gap is concerning given the increasing number of individuals covered by Medicaid since the start of health insurance expansion under the Affordable Care Act (ACA). By August 2018, there were over 73 million total Medicaid beneficiaries, which included the more than 15 million individuals newly enrolled in Medicaid since the first Marketplace opened in 2013 (Medicaid.gov, 2018). However, once insurance coverage is ensured for patients, there still remains the potential barrier of accessing care at the practice level. Research finds that Medicaid patients constitute less than 10% of a physician’s patient panel, and many physicians report not accepting new Medicaid patients (Hing et al., 2015; Neprash, Zink, Gray, & Hempstead, 2018). Workforce challenges, such as current and projected provider shortages, as well as geographic maldistribution of providers to areas of need, have increased interest in the greater use of nurse practitioners (NPs) in the ambulatory setting to deliver care, especially for the most vulnerable populations (Maier, Aiken, & Busse, 2017). It is known that NP employment in physician practices has increased in recent years (Barnes, Richards, McHugh, & Martsolf, 2018; Martsolf et al., 2018); thus, the use of NPs within physician practices is one workforce intervention that can be deployed to improve access to care for Medicaid beneficiaries. Buerhaus, DesRoches, Dittus, and Donelan (2015) found that primary care physicians who work with NPs were more likely to accept new Medicaid patients than physicians working in practices without NPs. Additionally, there is evidence of greater appointment availability for Medicaid patients in physician practices that employ NPs (Richards & Polsky, 2016; Tipirneni et al., 2016). However, there have been no examinations of whether the employment of NPs within physician practices is associated with greater Medicaid acceptance over time. The purpose of this study was to examine the association between physician practice Medicaid acceptance and NP employment. This longitudinal study was a secondary analysis of a national panel of 102,453 physician practices from 2009-2015. The primary data sources used for this study were the SK&A physician and nurse files. SK&A (IQVIA, 2018) is a commercial market research firm that maintains data sets of office-based healthcare providers; these data are updated twice-yearly via telephone-verification. A strength of these data is that we were able to identify individuals, most importantly individual NPs, employed in each practice in a given year. We were also able to determine Medicaid acceptance for these same practices during the study period. County-level characteristics (i.e., control variables in our models) of each practice location were obtained from the Area Health Resource File (Health Resources and Services Administration, n.d.). To examine our main association of interest, we employed a practice-level fixed effects (FE) linear regression model. The practice FEs allowed us to capture changes in Medicaid acceptance and NP presence within the same practice over time. We included year FEs, and robust standard errors were clustered at the practice level. To explore any variation in the outcome across different types of practices, we stratified our sample by “small” (<4 physicians) and “not-small” (4+ physicians) practices. Across all practices, a greater percentage of not-small practices accepted Medicaid if they employed at least one NP (78.8%) compared to not-small practices that did not employ any NPs (73.4%). A similar pattern was seen among small practices with 68.4% of practices with NPs accepting Medicaid compared to small practices with no NPs (59.2%). We then leveraged the complete panel of physician practices to examine the potential influence of incorporating NPs into a practice with Medicaid acceptance. In our adjusted models, across all practices, employing 1 or more NPs was associated with a statistically significant 0.5-percentage point (p < .05) increase in the probability of a practice accepting Medicaid. When we stratified our sample by small and not-small practices, there was a 0.7-percentage point (p < .05) increase in the likelihood that a small physician practice accepted Medicaid; however, the relationship was non-significant among not-small physician practices suggesting that NP employment may be more important for small physician practices and whether that practice accepts Medicaid. Additional analyses revealed a statistically significant influence of NP employment (β = 0.010, p < .05) on Medicaid acceptance among medical sub-specialty practices, but the relationship was non-significant among primary care, surgical specialties, and multispecialty physician practices. Finally, we looked at Medicaid acceptance by whether the state where the practice was located adopted Medicaid Expansion at any time under the ACA. The results for both categories (i.e., expansion and non-expansion states) were non-significant suggesting that Medicaid Expansion seemed to have no bearing on the relationships between NP presence and practice Medicaid acceptance. In summary, we found a positive and statistically significant relationship between NP employment and practice Medicaid acceptance, which indicates that there is an important role for NP employment in physician practices for potentially improving access to care for those individuals covered by public insurance programs and perhaps for those populations, who traditionally struggle to access care. Within the broader context of healthcare delivery, we found a significant and strong relationship between NP employment and Medicaid acceptance among medical practices. Many physician practices geared toward sub-specialty care are increasingly embracing roles for NPs (Brush et al., 2015; Castellucci, 2017). Doing so is believed to enhance care delivery and expand workforce capabilities in these specialized settings. Finally, these findings have implications internationally for improving access to care among vulnerable patient populations as the number of NPs is also increasing abroad (Maier, Barnes, Aiken, & Busse, 2016), and healthcare leaders are exploring ways to leverage the existing and growing NP workforces to improve care delivery and access (Maier et al., 2017). Employing NPs is a viable way for practices to expand their capacity and improve access to care.