Case fatality and population mortality associated with anaphylaxis in the United States

Anaphylaxis is a serious allergic reaction that can cause death; however, the actual risk of death is unclear.

We sought to estimate the case fatality rate among hospitalizations or emergency department (ED) presentations for anaphylaxis and the mortality rate associated with anaphylaxis for the general population.

This was a population-based epidemiologic study using 3 national databases: the Nationwide Inpatient Sample (NIS; 1999-2009), the Nationwide Emergency Department Sample (NEDS; 2006-2009), and Multiple Cause of Death Data (MCDD; 1999-2009). Sources for these databases are hospital and ED discharge records and death certificates, respectively.

Case fatality rates were between 0.25% and 0.33% among hospitalizations or ED presentations with anaphylaxis as the principal diagnosis (NIS+NEDS, 2006-2009). These rates represent 63 to 99 deaths per year in the United States, approximately 77% of which occurred in hospitalized patients. The rate of anaphylaxis-related hospitalizations increased from 21.0 to 25.1 per million population between 1999 and 2009 (annual percentage change, 2.23%; 95% CI, 1.52% to 2.94%), contrasting with a decreasing case fatality rate among hospitalizations (annual percentage change, -2.35%; 95% CI, -4.98% to 0.34%). Overall mortality rates ranged from 0.63 to 0.76 per million population (186-225 deaths per year, MCDD) and appeared stable in the last decade (annual percentage change, -0.31%; 95% CI, -1.54% to 0.93%).

From 2006 to 2009, the overwhelming majority of hospitalizations or ED presentations for anaphylaxis did not result in death, with an average case fatality rate of 0.3%. Anaphylaxis-related hospitalizations increased steadily in the last decade (1999-2009), but this increase was offset by the decreasing case fatality rate among those hospitalized; both inpatient and overall mortality rates associated with anaphylaxis appeared stable and were well under 1 per million population. Although anaphylactic reactions are potentially life-threatening, the probability of dying is actually very low. With the prevalence of anaphylaxis on the increase, practitioners need to stay vigilant and follow the treatment guidelines to further reduce anaphylaxis-related deaths.