Findings from a study published in the Annals of Allergy, Asthma & Immunology suggest the ongoing difficulty in diagnosing anaphylaxis as evident by the low prescribing rates of epinephrine auto-injector in cases of anaphylaxis.

Estimates on the incidence of anaphylaxis are insufficient and the current International Classification of Diseases, Ninth Revision (ICD-9) codes present a challenge in accurately diagnosing anaphylaxis and assessing epinephrine prescribing. Study authors aimed to calculate the incidence and and demographics of patients with anaphylaxis-related ICD-9 codes in a large health maintenance organization and to analyze rates of epinephrine prescribing and dispensing. 

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Eligible patients had at least 12 months of continuous membership from January 1, 2008 to December 31, 2012 and were chosen based on anaphylaxis-related ICD-9 codes (n=159,172). The final analysis included 52,045 patients after excluding individual chart reviews with expanded ICD-9 codes representing unconfirmed anaphylaxis cases. 

The data showed that the incidence of anaphylaxis over the 4-year period was 2.07% with a higher prevalence in females vs. males (56.5% vs. 43.5%). Of the total cases, epinephrine was prescribed in 16.2%. The highest rates of epinephrine prescription were for the ICD-9 codes 995.0 (other anaphylactic shock) and 995.60 to 995.69 (anaphylactic shock caused by food) at 49.3% and 58.6%, respectively. Epinephrine auto-injectors were dispensed 95.9% of the time when prescribed regardless of the copay amount. 

Study authors concluded that the continued difficulty in diagnosing anaphylaxis “could result in suboptimal treatment of potential future episodes.” 

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