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Methods for Computing PCP Need

Service Areas

Every method for computing the need for Primary Care Physicians in Alabama must start by defining a collection of service areas that partition the state. The assumption is that patients in a service area will seek care from a PCP in that service area. The service areas could possible be

  1. Counties

  2. ZIP Code Areas

  3. Census Tracts

  4. PCSAs

Counties are most commonly used, but are perhaps too coarse. ZIP code areas and census tracts are too fine. All of the first three are artificial, based on boundaries that have nothing to do with healthcare. PCSAs are the most rational and have the proper resolution. The various area layers can be viewed in the interactive map.

Models

After defining service areas, the next step is a computational model for determining the number of PCPs needed for the service area, and then comparing that with the number of PCPs present in the service area.

Ratio Models

The most common model for determining need is based on computing Population to PCP ratio or PCP to Population ratio in the service area. The various ratio methods are equivalent. In this presentation, we use the number of PCPs per 10,000 population so that the numbers are smaller and easier to understand. So for example, the need could be based on a desired PCP per 10K ratio of

  • 4.61, the national average, corresponding to a population to PCP ratio of 2169

  • 4.00, corresponding to a population to PCP ratio of 2500

  • 3.33, corresponding to the HRSA recommendation of a population to PCP ratio of 3000

Supply and Demand Models

Another method is to compute the demand for PCP services, based on the demographics of the service area, and the supply of PCP services, based on the number of PCP FTEs in the service area. Both supply and demand can be based on time or visits (or perhaps other metrics).

Demand Table

The following table gives the mean and the standard error of the number of visits per year (VPY) to a primary care physician (PCP) and the time (in minutes) per visit (MPV) for various age groups. The data are from the National Ambulatory Medical Care Survey, published by the Centers for Disease Control.

Need Based on Visits

The total average number of PCP visits needed per year for a service area can be computed by multiplying the population in each age group by the mean visits per year for that age group, and then summing over the 13 age groups. This gives the demand for the service area in visits per year. On the other hand, on average, an FTE PCP sees 20 patients per day, 5 days per week, for 48 weeks per year, for a total of 4800 visits year. This is the supply in visits per year per FTE. The FTE need for a service area is computed by dividing the total number of visits required by the population in a year by 4800, the average number of visits an FTE can supply in a year. Finally then the difference between the FTEs present in the PCSA and FTEs needed is either the surplus (if positive) or deficiency (if negative).

Need Based on Time

The total average PCP time needed per year for a service area can be computed by multiplying the population in each age group by the mean visits per year and by the mean time per visit for that age group, and then summing over the 13 age groups. This gives the demand for the service area in minutes per year. On the other hand, on average, an FTE PCP works 8 hours per day, 5 days per week, and 48 weeks per year, for a total of 115,200 minutes of patient time per year. This is the supply in minutes per year per FTE. The FTE need for a service area is computed by dividing the total time required by the population in a year by 115,200, the average yearly patient time of an FTE. Once again, the difference between the FTEs present in the PCSA and the FTEs needed ie either the surplus (if positive) or the deficiency (if negative).

Alabama Primary Care Service Areas

Statewide primary care service areas (PCSAs) developed by the Office for Family Health, Education & Research (OFHER) are presented in this policy brief, by means of interactive maps using Geographical Information System (GIS) software, and by means of interactive tables.

Background

The U.S. Department of Health and Human Services Health Resources & Services Administration Bureau of Health Workforce Division and Shortage Designation is requiring all State Primary Care Offices to establish Rational Service Area Plans covering their entire state/territory by 2022. States are allowed four years to accomplish this project (2019–2022).

The description of a rational service area was introduced in the State Health planning Act of 1974. Section 332. [254e] (a) (1) of the Public Health Service Act designates Health Professional Shortage Areas as an urban or rural area (which need not conform to the geographic boundaries of a political subdivision and which is a rational service area of the delivery of health care services).

Federal Register Volume 63 September 1998 in the section Proposed Rules for Designation of Health Professional Shortage Areas (HPSA) and Medically Underserved Areas and Populations (MUA/P) includes a statement that States will be encouraged to define a complete set of rational service areas covering its territory.

A rational service area for primary care, a PCSA, is a relatively self-contained primary care geographic unit that reflects utilization patterns for primary care. In other words, it is an area within which most residents could or do seek and obtain most of their primary health care services.

The purpose of establishing PCSAs is to enhance the ability of states to better identify their primary care health needs and explore ways to meet those needs at functional geographic levels.

Guidelines for Primary Care Service Areas

There are seven criteria for PCSAs that are commonly specified in federal publications, published articles, and reviewed in detail in the 2000 Bureau of Primary Health Care Report:

  1. Account for existing primary care providers (primary care physicians).

  2. Have a defined service area access of 30 minutes or less drive time to population centers.

  3. Have hospital availability.

  4. Be able to identify the population and population demographics of the PCSA population.

  5. Be able to identify populations outside of the PCSA catchment areas.

  6. Consider historical relationships among communities.

  7. Consider non-medical services, commuting and shopping patterns.

The Office of Family Health Education & Research developed a set of 79 non-overlapping PCSAs that cover Alabama. These PCSAs are based on population centers that are 30 minutes or more driving time to other population centers. These population centers and /or general admission hospitals (GAHs) serve as centroids. Each PCSA consists of the region of the state that is closer to that centroid than any other, as measured by the road network.

General Conclusions

Using PCSAs instead of counties, ZIP codes, and/or Rural-Urban Commuting Area (RUCA) codes leads to databases that are based on non-restricted, non-artificial, but geographically limited populations with identifiable demographics. PCSAs allow the ability to identify and measure the primary care needs of populations in geographical areas in term of accesible healthcare resources and assets. In our case, Alabama PCSAs allow us to measure a defined population's accessibility to designated population centers where PCPs and GAHs are located and to estimate local PCP shortages or oversupply.

Our PCSAs rural/urban designations use the Centers for Medicare & Medicaid Services definition of rural based on the National Census Bureau urban-centric concept.

Alabama's PCSAs when used to define Health Professional Shortage Areas produce accurate data for linking PCP availability to population demand, HIPSA standard or PCP population ratio. Using PCSAs is a functional alternative to designating partial counties as rural or urban. It eliminates the necessity of trying to determine the rurality of a political subdivision.

The use of PCSAs provides a foundation from which to build on our current primary care coverage and to pursue more in-depth analysis of workforce issues and barriers to primary care access based on the rationally determined micro-populations at individual sites. This model gives the definition and focus for developing public and private partnerships, rural public policy, legislative support, pilot projects, and rural outcome research.

Strategies

  1. Use Alabama Rational Service Areas as the geographic unit for documenting primary care physician distribution, workforce analysis and projections.

  2. Use the population centers of Alabama's Rational Service Areas as centroids for health care services.

  3. Use Alabama Rational Service Areas at the geographic unit for documentation, and analysis for the delivery of health care services.

Definitions and Methods

Primary Care Physician (PCP)

In this report, a primary care physician is as non-federal allopathic (MD) or osteopathic (DO) physician, who holds an unrestricted license to practice medicine in the state of Alabama, is providing direct patient care and practices principally in one of the five primary care specialties—general medicine, family medicine, general internal medicine and pediatrics and Med-Peds. Since the foot print of Med-Peds licensed physicians is so small they are counted with family physicians. PCPs engaged solely in administration, emergency medicine, emergency/urgent Care, research, sports medicine, teaching, telemedicine, or are hospitalist, retired physicians who hold unrestricted licenses, federal physicians (VA physicians) and federal and state prison physicians are not counted.

Full-Time-Equivalent Primary Care Physician (FTE/PCP)

A 40 hour work week is used as the standard for counting a PCP as a 1.0 FTE/PCP. Each PCP reporting direct patient care for 40 hours or more per week are counted as 1.0 FTE. Those PCPs who are not available for direct patient care to residents in their area for 40 hours per week, have their FTE figure determined by the counting a 0.1 FTE for each 4 hours or 1/2 day that they are available. PCP data presented as FTE/PCP, such as the number of PCPs located in each PCSA are tallied by determining the FTE of each PCP in a given PCSA. Any physician data not identified as FTE physician data considers each physician as 1.0 FTE.

In addition the following adjustments were made to the PCP count: Those residents in training with significant direct patient care time in an ambulatory setting were counted as 0.1 FTE/PCP. Faculty with significant practice and teaching time in an ambulatory setting were counted at 0.5 FTE/PCP.

Rational Service Area for Primary Care (PCSA)

A rational service area is a relatively self-contained geographic area that reflects utilization patterns for primary care. More simply stated, it is an area within which most residents could or do seek to obtain direct patient access to a PCP(s). Each PCSA includes a population center. Alabama has 79 population centers where in 2019 97.8% of Alabama’s PCPs practice sites are located. Each PCSA population center historically has had the ability to recruit PCPs. These population centers are spatially located such that 96% of Alabama’s 4,850,771 residents have 30 minute of less travel time access to PCPs.

Rural/Urban

The 79 PCSA population centers (the geographic locations where most residents in a PCSA catchment area could or do seek to obtain direct patient access to a PCP) are designated rural or urban using the Centers for Medicare and Medicaid Services (CMS) definition of rural. A rural area is an area that is not delineated as an urbanized area by the Bureau of the Census. This definition is used by CMS to assess if a rural health clinic’s location meets their requirement of being located in a rural area.

CMS defines a urbanized areas as central cities of 50,000 inhabitants or more or cities with at least 25,000 inhabitants which, together with contiguous areas having stipulated population density, have combined populations of 50,000 and constitute, for general economic and social purposes, single communities and closely settled territories surrounding cities and specifically designated by the Census Bureau as urban.

Rural Population Center

A rural population center is a city, town or community not located within an urbanized area where rural residents do or could access PCPs and because of topography, market or transportation patterns, distinctive population characteristics or other factors, has limited access to contiguous population centers as measured generally by a travel time of greater than 30 minutes to such population centers.

Urban Population Center

Established neighborhoods and communities within urbanized areas where residents generally located within 30 minutes of less do or could seek access to PCPs and which display a strong self-identity (as indicated by a homogeneous socioeconomic or demographic structure and/or a tradition of interaction or interdependency), have limited interaction with contiguous populations centers and which have a minimum population of 20,000. Urban catchment areas do not recognize urbanized area boundaries.

Population Count

Population count is the total permanent resident civilian population within the catchment area of the PCSA, excluding inmates of institutions.

Population per PCP Ratio

The ratio of the number of PCSA residents to a PCP is calculated using the FTE/PCP count.

Current PCP Need

The number of PCP/FTEs needed to serve a given PCSA is determined by comparing the average number of PCP vists per year needed by the population with the average number of patient visits that a PCP can provide. A more detailed explanation is given in the data table page.

About OFHER

The Office for Family Health Education and Research provides an infrastructure where opportunities for research in education, policy, clinical medicine and other scholarly works in primary care can flourish. The office produces and disseminates practical clinical information to primary care physicians, coordinates and conducts studies that deal with the health care education of primary care physicians and patients, as well as the broader issues of state health policy, health access and health manpower.