Abstract
The United States faces a critical policy question: Does digital prior authorization reduce administrative burden, or does it amplify existing mechanisms of coverage denial and exclusion? This study combines a newly compiled pre-implementation dataset of 32 payer-program disclosures for the year 2025 with a prespecified causal framework for evaluating Fast Healthcare Interoperability Resources (FHIR)-based prior authorization following verified production implementation. The year 2025 baseline includes 4,963,129 standard requests and 757,804 expedited requests among observations with disclosed denominators. The unweighted mean standard denial rate was 13.68%, whereas the request-weighted rate was 3.71%, demonstrating substantial concentration in large, low-denial contracts. Mean standard decision time was positively associated with denial rate (Pearson r = .63, p < .001). In a heteroskedasticity-adjusted exploratory model controlling for broad program type, each additional reported day of standard decision time was associated with a 4.86-percentage-point higher denial rate (95% CI [2.38, 7.34]). These cross-sectional associations are noncausal and do not estimate the effects of FHIR adoption. The proposed 2024–2030 payer-provider panel distinguishes the January 2026 process and transparency requirements from the principal January 2027 API implementation requirements. It incorporates verified production go-live dates, electronic transaction shares, and contemporary staggered difference-in-differences and event-study estimators. Outcomes include authorization speed, information requests, denials, appeals, authorization-related claim denials, accounts-receivable duration, cash conversion, treatment delays, abandonment, and equity. The study establishes a reproducible pre-implementation benchmark and a rigorous framework for determining whether interoperability reduces transaction costs and improves access or instead accelerates exclusion.