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The Impact of Primary Care Clinician Staffing Mix on Quality

Huang PY, Yano EM, Lee ML, Rubenstein LV. The Impact of Primary Care Clinician Staffing Mix on Quality. Paper presented at: Society of General Internal Medicine Annual Meeting; 2002 May 1; Atlanta, GA.


BACKGROUND Managed care organizations, including the VA, increasingly employ nurse practitioners (NPs) and physician assistants (PAs) in addition to physicians (MDs) as primary care (PC) providers. Research shows that non-physician clinicians (NP/PAs) provide high quality PC, but these studies evaluated NP/PA care for specific patients under specific practice conditions, rather than the impact of staffing structure. We examined the effect of the NP/PA-to-MD staffing ratio on the quality of primary care. METHODS We surveyed the PC practice leaders of all 170 VA medical centers (VAMC) in 1999 (94% response rate). We used survey and VA computer administrative data to measure facility characteristics (e.g., facility complexity, academic affiliation) and PC practice characteristics (e.g., firm system practice arrangement, use of managed care arrangements such as guidelines and provider education). Survey data for each VAMC was linked to 1999 PC practice outcomes as measured by performance measures for patient satisfaction, preventive care, and chronic disease management. The VA calculates performance measures yearly based on randomly selected patients visiting PC through: (1) the VHA National Ambulatory Care Survey, a national VA patient satisfaction survey, and (2) the Prevention Index (PI) and Chronic Disease Index (CDI), from the chart-based VHA External Peer Review Program. The NP/PA-to-MD ratio for each facility was calculated by dividing the number of PC NP/PAs by the number of PC MDs. We transformed the NP/PA-to-MD ratio and dependent variables (practice outcomes), and performed multivariate regression to predict the influence of the NP/PA-to-MD ratio on practice outcomes, adjusting for facility and PC practice characteristics. RESULTS Overall, 148/154 (96%) of VAMC PC practices reported using NP/PAs as PC providers; mean NP/PA-to-MD ratio 0.75. Academic VAMCs, practices with PC training programs, or with more provider education had higher NP/PA-to-MD ratios. In bivariate regressions, a higher NP/PA-to-MD ratio was associated with worse PI and CDI scores, but better patients┬┤ ratings of emotional support (p < 0.05). After controlling for facility and practice characteristics, a higher NP/PA-to-MD ratio remained independently associated with lower PI and CDI scores and greater patient satisfaction with emotional support (p < 0.05). CONCLUSION Contrary to expectations, VA PC practices with higher NP/PA-to-MD staffing ratios performed worse than those with lower ratios on measures of preventive and chronic disease care. Future research should investigate whether the lower PI/CDI scores reflect problems with NP/PA roles within these PC practices (e.g., inadequate visit duration, excessive patient complexity) or whether they reflect structural deficiencies affecting the quality of both MD and NP/PA clinical work. Continued addition of NP/PAs to these practices without new approaches to practice design will unlikely yield higher PI/CDI socres. More information on clinician staffing models is needed.

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