During the largest epidemiological analysis of meningitis and encephalitis conducted in the United States, researchers found that the majority of cases were initially treated with antibiotic therapy even though most illnesses were caused by viruses.
In addition, Rodrigo Hasbun, MD, MPH, associate professor of infectious diseases at UTHealth McGovern Medical School, and colleagues reported that adjunctive steroid use was underused in patients with pneumococcal meningitis despite its association with reduced mortality in this population.
“Meningitis and encephalitis in the U.S. remain a challenging syndrome to clinicians, with the majority of patients being admitted to the hospital and receiving empirical antimicrobial therapy pending identification of the causative agent,” the researchers wrote in Clinical Infectious Diseases. “Earlier identification of the etiologic agents could aid clinicians in better selecting their empirical therapy choices in the future.”
Hasbun and colleagues examined data from the Premier Healthcare Database, which contains information on more than 619 million patient visits, or one in every five hospital discharges in the United States. Their analysis included 26,429 adult patients (53.3% female; median age, 43 years) who were diagnosed with meningitis or encephalitis between January 1, 2011 and December 31, 2014.
According to the data, the most common cause of illness was enterovirus (50.9%), followed by unknown etiologies (18.7%), bacterial meningitis (13.9%), herpes simplex virus (HSV; 8.3%), noninfectious etiologies (3.4%), fungal infections (2.7%), arboviruses (1.1%) and other viruses (0.8%). Overall, 85.5% of patients received antibiotics, 53.4% received antivirals, and 7.8% received antifungal therapies. Among patients with viral etiologies, antibiotics were administered to 89% of those with enterovirus, 84.7% with herpes viruses, 92.4% with arboviruses, and 87.3% with other viruses. The median duration of antibiotic therapy among these patients ranged from 3 to 7 days.
Adjunctive steroid use was documented in 15.9% of patients, ranging from 10.1% among patients with fungal meningitis to 39.3% among those with pneumococcal meningitis. Although the compliance rate was low, the researchers reported that adjunctive steroids reduced mortality only in patients with pneumococcal meningitis (6.7% vs. 12.5%; P = .02).
“Adjunctive steroids are not indicated in viral etiologies and can be harmful in fungal meningitis by increasing disability, side effects and affecting microbiological clearance,” the researchers wrote. “Despite this, 10.1% of fungal cases of meningitis received inappropriately intravenous steroids, which may be associated with a trend towards an increased rate of mortality (13.7% vs. 7.6%).”
When looking at patient outcomes, the researchers found that, overall, the median length of hospital stay was 4 days, the 30-day readmission rate was 3.2% and the inpatient mortality rate was 2.9%. The worst outcomes were among patients with bacterial meningitis (7-day median length of stay; 6.7% 30-day readmission rate; and 8.2% mortality rate), fungal meningitis (13-day length of stay; 5.4% 30-day readmission rate; and 8.2% mortality rate), arboviruses (10-day length of stay; 12.7% 30-day readmission rate; and 8.9% mortality rate), and other viruses (8-day length of stay; 6.1% 30-day readmission rate; and 11.7% mortality rate).
The researchers noted that although the overall mortality rate was low, 17.4% of patients were discharged to a nursing home, rehabilitation facility or hospice. They concluded that their study had several limitations, including the reliance of ICD-9 diagnosis codes in hospital discharge data, the potential misclassification of etiologies, and limited clinical data.
“Despite these limitations, our study had several advantages,” they wrote. “This is the first study to report on the use of antimicrobial therapies and adjunctive steroids by different etiologies. It is also the first study to evaluate the impact of adjective steroids on mortality in the U.S.” – by Stephanie Viguers
Hasbun and two other colleagues report being paid consultants for bioMérieux, which funded the study.