Costs and Outcomes Associated With Invasive Aspergillosis Infections

Despite being a rare disease, invasive aspergillosis (IA) is still associated with increased hospital mortality and 30-day readmission rates, and excess duration of hospital stay and costs that may reach up to $600 million annually, according to research in Clinical Infectious Diseases.

In order to assess the mortality and morbidity burden in the United States, researchers analysed data from the Health Care Utilization Project to compare characteristics and outcomes between patients with and without IA.

Investigators identified 66,634,683 discharged patients who met the study criteria, of whom 154,888 (0.2%) had a diagnosis of IA. Common high-risk conditions for IA were major surgery (50.1%) in the non-IA group and critical illness (41.0%) in the IA group.

Propensity score matching found that both mortality (odds ratio [OR] 1.43; 95% CI, 1.36-1.51) and 30-day readmission (OR 1.39; 95% CI 1.34-1.45) rates were higher in the IA group. Furthermore, IA was also associated with 6.0 (95% CI, 5.7-6.4) excess days in the hospital and $15,542 ($13,869 to $17,215) in extra costs per hospitalization.

The study results revealed an increase in prevalence of IA in patients undergoing acute hospitalizations; however, this may be attributable to improved diagnostics and increased use of immunosuppressive therapies and organ transplants. 

The study was also limited by the use of administrative codes rather than clinical data to identify high-risk groups and IA, which may have introduced classification errors in the case definitions. Investigators were also unable to determine temporal connections between high-risk conditions and IA and to pinpoint time of IA onset. 

Thus,  some of the observed increases in length of stay and cost may in fact be a risk factor for IA rather than a consequence. Finally, treatment information was not available and therefore its potential impact on outcomes is unknown.

The investigators were able to conclude that “although rare even among high-risk groups, IA is associated with high hospital mortality rates, excess duration of hospitalization, and a 40% relative increase in the odds of 30-day readmission.” 

In the United States, 40,000 annual IA admissions occur, which at an excess cost of $15,000 means “the aggregate IA-attributable excess costs in the United States may reach $600 million annually.”

Disclosure: This work was supported by Astellas Pharma and by the medical and development division of Astellas, Astellas Pharma Global Development.

Reference

Zilberberg MD, Nathanson B, Harrington R, Spalding J, Shorr AF. Epidemiology and outcomes of hospitalizations with invasive aspergillosis in the United States, 2009–2013 [published online April 28, 2018]. Clin Infect Dis. doi:10.1093/cid/ciy181