Accuracy of ICD-10 Coding for Anaphylaxis

Rationale: ICD-10 is the classification system used most often by allergists worldwide. It has been used as a proxy for anaphylaxis cases in retrospective studies. However, it is not considered appropriate for clinical practice. The objective of this study was to determine the accuracy of ICD-10 coding for anaphylaxis in an emergency department (ED).

Methods: We performed a 5-year retrospective chart review from 2010 to 2014 of patients under the age of 18 years who were diagnosed at the ED with ICD-10 codes T78.0-T78.4. All charts were reviewed to identify anaphylaxis by using the World Allergy Organization (WAO) anaphylaxis clinical diagnostic criteria as the gold standard. A positive predictive value was calculated for ICD-10 codes T78.0-T78.2 which are the codes to diagnose anaphylaxis. A negative predictive value was calculated for ICD-10 codes T78.3-T78.4 which are the codes to diagnose angioedema and allergy (unspecified). 

Results: A total of 379 ED patients with ICD-10 codes T78.0-T78.4 were reviewed. We found 82 patients who met the anaphylaxis diagnostic criteria by WAO. Sixty-nine medical records with ICD-10 codes T78.0-T78.2 had a positive predictive value of 88.4% (95% CI 78.7 to 94.0). The negative predictive value of 310 medical records with ICD-10 codes T78.3-T78.4 was 93.2% (95% CI 89.8 to 95.5). 

Conclusions: ICD-10 coding for anaphylaxis had high positive and negative predictive values.