A comparison of methods for measuring spatial access to health care

Abstract

Objective To compare measures of spatial access to care commonly used by policy makers and researchers with the more comprehensive enhanced two‐step floating catchment area (E2SFCA) method. Study Setting Fourteen southwestern Pennsylvania counties. Study Design We estimated spatial access to buprenorphine‐waivered prescribers using three commonly used measures—Euclidean travel distance to the closest prescriber, travel time to the closest provider, and provider‐to‐population ratios—and the E2SFCA. Unlike other measures, the E2SFCA captures provider capacity, potential patient volume, and travel time to prescribers. Data Collection/Extraction Methods We measured provider capacity as the number of buprenorphine prescribers listed at a given address in the Drug Enforcement Agency's 2020 Controlled Substances Act Registrants Database, and we measured potential patient volume as the number of nonelderly adults in a given census tract as reported by the 2018 American Community Survey. We estimated travel times between potential patients and prescribers with Bing Maps and Mapbox application programming interfaces. We then calculated each spatial access measure using the R programming language. We used each measure of spatial access to identify census tracts in the lowest quintile of spatial access to prescribers. Principal Findings The Euclidean distance, travel time, and provider‐to‐population ratio measures identified 48.3%, 47.2%, and 69.9% of the census tracts that the E2SFCA measure identified as being in the lowest quintile of spatial access to care, meaning that these measures misclassify 30%–52% of study area census tracts as having sufficient spatial access to buprenorphine prescribers. Conclusions Measures of spatial access commonly used by policy makers do not sufficiently accurately identify geographic areas with relatively low access to prescribers of buprenorphine. Using the E2SFCA in addition to the commonly used measures would allow policy makers to precisely target interventions to increase spatial access to opioid use disorder treatment and other types of health care services.

Disparities in Spatial Access to Emergency Surgical Services in the US

“…Using metrics that incorporate population demand and measures of hospital capacity, this study raised concerns that using measures of travel distance or time alone might underestimate the proportion of the US population that experiences limitations in access to surgical care-using E2SFCA models, nearly 10% had low access to any surgical hospital, and 21% had low access to advanced-resource centers. This discordance aligned with our prior work 17 assessing spatial access to EGS hospitals in California and the recent findings of Drake et al, 9 who directly compared the E2SFCA with travel impedance measures of spatial access to buprenorphine prescribers and found that standard metrics (impedance measures and physician-to-population ratios) identified less than half of low-access census tracts compared with E2SFCA models.…”

Disparities in geographic access to medical oncologists

“…These threshold drive times are broadly consistent with CMS Medicare Advantage network adequacy standards. 29 Next, we used an E2SFCA method 16,30 to measure geographic access to medical oncologists. The E2SFCA simultaneously accounts for provider capacity, patient demand, and travel time facing patients.…”

“…We provide a more detailed description of the E2SFCA approach and weighting in the technical appendix (Data S2). For further discussion of the E2SFCA measure, see Luo and Qi 16 and Drake et al 30 For further discussion of the weight approach, see Kwan, 31 Wang, 33 and Drake et al 30 We grouped RUCA codes into three categories of rurality: urban (RUCA codes 1-3), large town (RUCA codes 4-6), and rural (RUCA codes 7-10). We aggregated national ADI rankings of census block groups to the census tract level based on the mean rankings for census block groups within a census tract.…”

“…Next, we used an E2SFCA method 16,30 to measure geographic access to medical oncologists. The E2SFCA simultaneously accounts for provider capacity, patient demand, and travel time facing patients.…”

“…We provide a more detailed description of the E2SFCA approach and weighting in the technical appendix (Data S2). For further discussion of the E2SFCA measure, see Luo and Qi 16 and Drake et al 30 For further discussion of the weight approach, see Kwan, 31 Wang, 33 and Drake et al 30 …”