title: Anaphylaxis in a health maintenance organization: International Classification of Diseases coding and epinephrine auto-injector prescribing.
abstract: BACKGROUND
  Accurate estimates of the incidence of anaphylaxis are limited. Current International Classification of Diseases, Ninth Revision (ICD-9) codes complicate accurate diagnosis of anaphylaxis and assessment of appropriate epinephrine prescribing.
  
  
  OBJECTIVE
  To quantify the incidence and demographic character of patients with anaphylaxis-related ICD-9 codes in a large health maintenance organization and analyze epinephrine prescribing and dispensing rates.
  
  
  METHODS
  All patients included had at least 12 months of continuous membership over a 4-year period from January 1, 2008 to December 31, 2012 and were selected based on anaphylaxis-related ICD-9 codes (N = 159,172). This algorithm was extrapolated from a previous study that used expanded ICD-9 codes to identify more cases of anaphylaxis. Individual chart reviews found that many expanded ICD-9 codes represented unconfirmed cases of anaphylaxis and therefore were excluded, resulting in analysis of 52,405 patients.
  
  
  RESULTS
  Incidence of anaphylaxis over 4 years was 2.07%, with female predominance (56.5%) over male predominance (43.5%). Epinephrine was prescribed in 16.2% of total cases. Highest rates of epinephrine prescription were for traditional 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. Of the cases in which an epinephrine auto-injector was prescribed, it was dispensed 95.9% of the time, independent of copayment amount.
  
  
  CONCLUSIONS
  Low epinephrine auto-injector prescribing rates in cases of anaphylaxis suggest the continued difficulty in the diagnosis of anaphylaxis and could result in suboptimal treatment of potential future episodes.
authors.affiliation: Department of Allergy and Immunology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California. Electronic address: Deena.Pourang@gmail.com.
authors.forename: Deena
authors.initials: D
authors.lastname: Pourang
authors.affiliation: Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California.
authors.forename: Michael
authors.initials: M
authors.lastname: Batech
authors.affiliation: Department of Allergy and Immunology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California.
authors.forename: Javed
authors.initials: J
authors.lastname: Sheikh
authors.affiliation: Department of Allergy and Immunology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California.
authors.forename: Shefali
authors.initials: S
authors.lastname: Samant
authors.affiliation: Department of Allergy and Immunology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California.
authors.forename: Michael
authors.initials: M
authors.lastname: Kaplan
mesh_terms: D000465:Algorithms; D000707:Anaphylaxis / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D002140:California / Q000453:epidemiology; D016527:Drug Costs; D011307:Drug Prescriptions; D004837:Epinephrine / Q000008:administration & dosage; D005260:Female; D006279:Health Maintenance Organizations / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D038801:International Classification of Diseases; D008297:Male; D011159:Population Surveillance; D010818:Practice Patterns, Physicians'; D012189:Retrospective Studies; D012646:Self Administration
chemical_list: D004837:Epinephrine