Positive predictive value of ICD-10 codes to detect anaphylaxis due to vaccination: A validation study.

PURPOSE: To validate the use of selected International Classification of Disease Codes 10th revision (ICD-10) to predict (positive predictive value) anaphylaxis due to vaccination using emergency department (ED) data. METHODS: We conducted a retrospective study using ED encounter data from a large tertiary-care teaching hospital, Monash Medical Centre, Melbourne, Australia. We searched all ED encounters potentially due to anaphylaxis after vaccination, between 1 January 2010 and 31 December 2018, using ICD-10-CM codes T80.5, T80.6, T88.1, T88.6, and T78.2. Health records of potential cases were examined to determine if they met the Brighton Collaboration (BC) criteria for anaphylaxis. We calculated the PPV to evaluate the accuracy of the selected ICD-10-CM codes in predicting anaphylaxis due to vaccination. RESULTS: Of the 69 health records identified and reviewed, 29 (42.2%) met the criteria for anaphylaxis regardless of the cause, and 24.6% (17/69) of records were confirmed as anaphylaxis triggered by vaccination (low positive predictive value). However, of the 23 records identified using ICD-10-CM code T80.5, 22 were classified as anaphylaxis cases regardless of the cause, and 12 were anaphylaxis due to vaccination cases giving PPV of 95.7% and 52.2%, respectively. CONCLUSIONS: Given that there is no specific ICD-10-CM code for anaphylaxis due to vaccination, ICD-10-CM code T80.5 may be suitable to monitor anaphylaxis due to vaccination in the ED setting. The current study was conducted at a single centre and needs to be confirmed by future multicentre studies.