Delirium Coding

Delirium is Major

Most delirium is never diagnosed. One reason for this is that the Medicare Severity Diagnosis Related Groups (MS-DRG) from the US Centers for Medicare and Medicaid Services (CMS) provides a financial incentive to diagnose toxic or metabolic encephalopathy instead. A report published in 2022 used the IBM MarketScan database and found that diagnostic codes for encephalopathy are diagnosed far more often than those for delirium. We believe there is only one rational explanation for this disparity: just follow the money.

Beginning in 2023, the ADS spearheaded a petition to CMS, requesting that diagnostic codes for delirium be upgraded from complication or comorbidity (CC) to major complication or comorbidity (MCC) in the MS-DRG system. Ultimately, 11 medical organizations supported this request that delirium be on par with toxic and metabolic encephalopathy. The body of the petition was subsequently published, including an analysis of the National Inpatient Sample that revealed the same disparity that had previously been shown using the IBM MarketScan data.

CMS replied to this request in their 2025 FY Proposed Rule (search for “causally specified delirium”); however, their analysis ignored our arguments, relying solely on an analysis of the MedPAR file. The ADS continued its advocacy by responding the Proposed Rule emphasizing our original arguments and pointing to the fact that toxic and metabolic encephalopathy were performing very similar to the primary delirium diagnosis, F05. Additionally, ADS sought to link our response with the Age-Friendly Health Systems proposal, lest this disparity lead to further disparity in coding. Again, eleven medical organizations affirmed their support for our petition to reclassify delirium codes as MCC, with the American Society of Anesthesiologists voicing their support in a separate letter.

Unfortunately, CMS did not approve our request with the publication of the 2025 Final Rule (see comments beginning on page 69084 at the bottom of the 3rd column). What is clear from CMS’s lengthy response is that our request received considerable support, urging CMS to change delirium’s severity designation. We find the comments in response to our petition surprisingly unresponsive.

The organizations that joined with the ADS in support of this initiative together represent more than 100,000 members. Professional organizations representing nearly every specialty that delirium affects agrees: delirium is major.

• Academy of Consultation-Liaison Psychiatry
• American Academy of Neurology
• American Association for Geriatric Psychiatry
• American College of Chest Physicians
• American Delirium Society
• American Geriatrics Society
• American Psychiatric Association
• American Society of Anesthesiologists
• American Thoracic Society
• Association of Medicine and Psychiatry
• Nurses Improving Care for Healthsystem Elders
• Society of Critical Care Medicine
• Society of Hospital Medicine.

Despite this disappointing outcome, we at ADS are encouraged at how this initiative has brought together such a supportive and diverse range of organizations invested in advancing clinical care for our patients by recognizing the dire and broad-reaching impact of delirium.

ADS is immensely grateful to all the organizations who supported this cause alongside ADS. We also recognized that advocacy is a marathon, not a sprint. We at ADS continue our advocacy, pursuing every lead and opportunity to collaborate on initiatives big and small to advance the cause of delirium.

Onward!

American Delirium Society