Unintended Consequences of Health Care Reform: Impact of Changes in Payor Mix on Patient Safety Indicators.

Objective: To evaluate the impact of the Affordable Care Act's Medicaid expansion on patient safety metrics at the hospital level by expansion status, across varying levels of safety-net burden, and over time.

Summary Background Data: Medicaid expansion has raised concerns over the influx of additional medically and socially complex populations on hospital systems. Whether increases in Medicaid and uninsured payor mix impact hospital performance metrics remains largely unknown. We sought to evaluate the effects of expansion on Centers for Medicare and Medicaid Services-endorsed Patient Safety Indicators (PSI-90).

Methods: Three hundred fifty-eight hospitals were identified using State Inpatient Databases (2012-2015) from 3 expansions (KY, MD, NJ) and 2 nonexpansion (FL, NC) states. PSI-90 scores were calculated using Agency for Healthcare Research and Quality modules. Hospital Medicaid and uninsured patients were categorized into safety-net burden (SNB) quartiles. Hospital-level, multivariate linear regression was performed to measure the effects of expansion and change in SNB on PSI-90.

Results: PSI-90 decreased (safety improved) over time across all hospitals (-5.2%), with comparable reductions in expansion versus nonexpansion states (-5.9% vs -4.7%, respectively; P = 0.441) and across high SNB hospitals within expansion versus nonexpansion states (-3.9% vs -5.2%, P = 0.639). Pre-ACA SNB quartile did not predict changes in PSI-90 post-ACA. However, when hospitals increased their SNB by 5%, they incurred significantly more safety events in expansion relative to nonexpansion states (+1.87% vs -14.0%, P = 0.013).

Conclusions: Despite overall improvement in patient safety, increased SNB was associated with increased safety events in expansion states. Accordingly, Centers for Medicare and Medicaid Services measures may unintentionally penalize hospitals with increased SNB following Medicaid expansion.