By Carol A. Kemper, MD, FACP
Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center
SOURCE: Hansen MA, Hasbun R. US hospitalizations and 60-day readmission rates associated with herpes simplex virus encephalitis: Analysis of all cause readmissions and encephalopathy associated readmissions. Clin Infect Dis 2022;74:1174-1182.
Herpes simplex encephalitis (HSE) is the most common cause of infectious encephalitis in the United States, accounting for around 30% of all causes of infectious encephalitis in the United States. With the advent of antiviral therapy and improved diagnostic measures, mortality and morbidity have improved over the past few decades, but patients remain at risk for long-term neurologic sequelae and even relapse. These authors examined 60-day readmission data from the Nationwide Readmissions Database (NRD), which is part of the U.S. Healthcare Utilization Project. The NRD was established in 2010 and continues to collect data linking hospitalizations and rehospitalizations within each year based on specific patient identifiers. By 2017, 27 states were participating in the NRD.
Between 2010 and 2017, among 95 million hospitalizations, there were 10,272 HSE hospitalizations in persons ≥ 1 year of age, and 804 inpatient deaths (7.8%). Of those who survived, 28.1% were readmitted at least once within 60 days.
Of those who survived the index hospitalization, the average age was 59 years, slightly more than half were female (51.3%), and the average hospital stay was 13.2 days. One-third presented with fever (32%), new-onset seizure (27%), and/or aphasia (12.5%). More than half required care in the intensive care unit, and 15.8% were intubated. Compared with HSE cases with no readmission within 60 days, those readmitted were older (average age 62.4 vs. 57.9 years, P < 0.001), had longer lengths of stay (15.4 vs. 12.7 days, P < 0.001), and were more likely to be discharged to an outside facility or home health (72.9% vs. 58.9%, P < 0.001). Having left against medical advice or transferred/discharged to home health were predictors of re-hospitalization. Using all clinical diagnosis codes, the four most common reasons for readmission were renal disease, pulmonary disease, encephalopathy, and diabetes. For all readmissions, 20% were diagnosed with “encephalopathy;” cerebral edema coding at index hospitalization correlated with encephalopathy at readmission.
From 2010 to 2017, 7.8% of all hospitalizations with a primary diagnosis of HSE died, and two-thirds of survivors required transfer/discharge to an outside facility or home health. More than one in four survivors (28%) required rehospitalization within 60 days, and 4.6% of survivors were rehospitalized with a diagnosis of “encephalopathy.” As predicted, rehospitalization was more likely in older individuals, with longer hospital stays and more complex co-medical conditions.
While the NRD database uses patient identifiers to link hospitalizations, only diagnostic codes were available to identify persons with a diagnosis of HSE, and no laboratory/clinical confirmation was required. While nearly 1/20 patients were rehospitalized with “encephalopathy,” it is not clear what proportion was due to relapsed HSE encephalitis vs. other types of encephalopathy (i.e., septic, metabolic, or medication-related). It would have been interesting if this large database had allowed for an assessment of the type and duration of treatment, the use of adjuvant corticosteroids, and whether delays in initiation of antiviral treatment were factors for readmission.
Herpes simplex encephalitis (HSE) is the most common cause of infectious encephalitis in the United States, accounting for around 30% of all causes of infectious encephalitis in the United States. With the advent of antiviral therapy and improved diagnostic measures, mortality and morbidity have improved over the past few decades, but patients remain at risk for long-term neurologic sequelae and even relapse.
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