New York State cases of anaphylaxis in elderly patients from 2000 to 2010

Limited information is available on the effect of anaphylaxis, a severe, potentially life-threatening allergic reaction, in the elderly population.

To elucidate the frequency of anaphylaxis and the demographic characteristics of elderly patients admitted to New York hospitals from 2000 to 2010.

A retrospective analysis of hospitalized patients aged 65 years and older in New York from 2000 to 2010 was conducted using the Statewide Planning and Research Cooperative System, a statewide administrative database. Cases were identified using anaphylaxis International Classification of Diseases, Ninth Revision (ICD-9) codes or an ICD-9-based diagnostic algorithm incorporating the National Institutes of Allergy and Infectious Disease diagnostic criteria. The χ² test was used to measure the association between demographic characteristics and group membership. Regression was used to model group and age as a function of hospital rates.

A total of 3673 hospitalizations were analyzed. Anaphylaxis ICD-9 codes identified 1790 cases (48.7%), the algorithms identified 1701 cases (46.3.%), and 182 cases (5.0%) were identified by both. Hospitalization rates increased significantly during this period (P < .001). Women comprised 61.5% and people of white race comprised 69.8% of the sample. Distribution by age differed by ascertainment method (ICD-9 vs algorithm) among the early-old group (65-74 years of age; 53.8% vs 41.8%) and among the late-old group (≥85 years of age; 11.2% vs 19.3%).

Hospitalization rates and anaphylaxis cases increased during the study period among the hospitalized elderly population of New York. Relying on anaphylaxis ICD-9 codes alone missed approximately half of possible cases. The identification and possibly the effect of anaphylaxis among the elderly population may differ, depending on age, race, payer, New York County, and disposition.