SIIM-CAIMI: 20% of advanced imaging prior auth denials get overturned

PHILADELPHIA -- More prior authorization denials for advanced imaging are overturned compared to other health services, suggest findings presented at the Society for Imaging Informatics in Medicine (SIIM)-CAIMI 2026 meeting. 

About one in five of these denials are overturned upon independent review, about five times the number of overturned denials across all Medicare Advantage services, reported a team led by James Tyler Ng from Geisinger Commonwealth School of Medicine in Scranton, PA and colleagues in a poster study. 

“These are second-level appeals,” Ng and colleagues wrote. “Few denials are appealed and most appeals succeed at the plan level, so independent review entity (IRE) cases are doubly selected.” 

Medicare Advantage now covers most Medicare beneficiaries, with insurers making around 53 million prior authorization determinations in 2024 alone. With the higher volume of determinations, insurers are increasingly using algorithmic utilization management tools. 

However, imaging-specific denial patterns cannot be measured, with IRE decisions being the one public source that names denied services under appeal. Prior research suggests that radiation therapy and head and neck surgery have higher overturn rates. The researchers noted that advanced imaging has not been evaluated in this area, and that limited data exist that separate prior authorization from claim and cost-sharing appeals.  

Ng and colleagues examined the frequency of prior authorization denials for advanced imaging for Medicare Advantage plans. This includes CT, MRI, PET, and CT angiography (CTA) exams.  

The study included 9,160 prior authorization denials that went through IRE review. Analysis also included 378,538 general services and 367,192 non-imaging services that served as abstract and refined comparators. 

The team found that 20.5% of advanced imaging prior authorization denials were overturned upon appeal and IRE review compared to 4.1% of denials across all services. This corresponded to a risk ratio of 4.98 and a risk difference of 16.4 percentage points (p < 0.001). 

For analysis between the abstract and refined comparators, the team reported a risk ratio of 5.63.  

And between 2020 and 2024, the number of appeals decided by IRE increased from around 1,400 to over 2,000. However, the overturn rate remained steady. While this rate was 28.4% in 2020, it hovered between 16.0% and 22.7% from 2021 to 2024. 

The researchers cautioned that their results do not generalize to all denials. They recommended mandatory service-level reporting Medicare Advantage prior authorization outcomes. 

The team also called for independent evaluation of algorithms that are used to adjudicate advanced imaging, with the same pre-deployment testing and post-deployment monitoring expected of diagnostic AI tools.