California Workers’ Comp Independent Medical Reviews Trending up, Report Shows

The number of Independent Medical Review decision letters issued in response to California workers’ compensation medical disputes is trending up in the last few years after declining steadily from 2018 through 2022, a report out on Thursday shows.

IMR decision letters started increasing in 2023, 2024 and through the first quarter of 2025, according to the California Workers’ Compensation Institute.

However, the uphold rate for medical service modifications and denials remains close to 90%, according to CWCI.

CWCI’s latest review of IMR activity and outcomes examined 1.57 million IMR decision letters issued from 2015 through March in response to applications submitted to the state after a Utilization Review physician modified or denied a workers’ comp medical service request.

CWCI tracked the number of letters issued quarterly, determined the distribution and uphold rates for disputed treatment requests by type of medical service, measured IMR response times and calculated the percentage of IMRs associated with high-volume physicians.

IMR was introduced in 2013 as part of a sweeping workers’ comp reform in California. It was expected to reduce medical disputes by helping to ensure that workers’ comp treatment met evidence-based medicine standards.

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