Determinants of referral network size for screening colonoscopies in the Veterans Health Administration after the implementation of the MISSION Act

Abstract

Objective: To measure key characteristics of the Veterans Health Administration's (VHA) Community Care (CC) referral network for screening colonoscopy and identify market and institutional factors associated with network size.

Data sources: VHA electronic health records, CC claim data, and National Plan and Provider Enumeration System.

Study design: In this retrospective cross-sectional study, we measure the size of the VHA's CC referral networks over time and by VHA parent facility (n = 137). We used a multivariable linear regression to identify factors associated with network size at the market-year level. Network size was measured as the number of physicians who performed at least one VHA-purchased screening colonoscopy per 1000 enrollees at baseline.

Data extraction: Data were extracted for all Veterans (n = 102,119) who underwent a screening colonoscopy purchased by the VHA from a non-VHA physician from 2018 to 2021.

Principal findings: From 2018 to 2021, median network volume of screening colonoscopies per 1000 enrollees grew from 1.6 (IQR: 0.6, 4.6) to 3.6 (IQR: 1.6, 6.6). The median network size grew from 0.63 (IQR: 0.30, 1.26) to 0.92 (IQR: 0.57, 1.63). Finally, the median procedures per physician increased from 2.5 (IQR: 1.6, 4.2) to 3.2 (IQR: 2.4, 4.7). After adjusting for baseline market characteristics, volume of screening colonoscopies was positively related to network size (β = 0.15, 95% CI: [0.10, 0.20]), negatively related to procedures per physician (β = -0.12, 95% CI: [-0.18, -0.05]), and positively associated with the percent of rural enrollees (β = 0.01, 95% CI: [0.00, 0.01]).

Conclusions: VHA facilities with a higher volume of VHA-purchased screening colonoscopies and more rural enrollees had more non-VHA physicians providing care. Geographic variation in referral networks may also explain differences in the effects of the MISSION Act on access to care and patient outcomes.

Keywords: VA healthcare system; geographic factors/spatial factors/small area variations; health promotion/prevention/screening; healthcare organizations and systems; referrals and referral networks.