Inpatient Diagnosis of Delirium and Encephalopathy: Coding Trends in 2011-2018

Ten medical societies have called for scientific literature to integrate research on delirium and encephalopathy, while physicians continually debate how to accurately document diagnoses of acute confusional states.

To promote this integration, we evaluated trends in diagnoses of delirium and encephalopathy among hospitalized adults and physician specialties, incorporating transitions to the Diagnostic and Statistical Manual of Mental Disorders-5 and the International Classification of Disease, tenth edition.

Using the 2011-2018 IBM MarketScan datasets, we identified delirium/encephalopathy patients aged ≥18 years using International Classification of Disease 9/10 codes among hospitalized patients. We identified physician specialties associated with the hospitalization and comorbidities within one year before the diagnosis of delirium or encephalopathy. Log-binomial models were used to evaluate diagnostic trends, adjusting for age, gender, insurance, and comorbidities.

We identified 10,509 hospitalized patients with a diagnosis of delirium and 94,438 with encephalopathy between 2011 and 2018. Although the number of patients with either diagnosis increased over time, the use of delirium diagnosis was less than it was for encephalopathy compared with 2011 after adjusting for covariates (adjusted risk ratio 0.45; 95% confidence interval 0.43 to 0.48). During the 8 years, neurologists and internists increased their use of both diagnoses, whereas only psychiatrists increased their use of delirium. Family practice physicians and nurse practitioners presented no significant change in either diagnosis for this timeframe.

Our results suggest that refined diagnostic codes and criteria may alter trends among clinicians in diagnosing delirium and/or encephalopathy. Additional diagnostic clarity may be necessary to support refined diagnoses among family practice physicians and nurse practitioners.