Drug Hypersensitivity Reactions Documented in Electronic Health Records within a Large Health System.

BACKGROUND: Hypersensitivity reactions (HSRs) are immunologic responses to drugs. Identification of HSRs documented in the electronic health record (EHR) is important for patient safety.

OBJECTIVE: To examine HSR epidemiology using longitudinal EHR data from a large United States healthcare system.

METHODS: Patient demographic information and drug allergy data were obtained from the Partners Enterprise-wide Allergy Repository (PEAR) for two large tertiary care hospitals from 2000 to 2013. Drug-induced HSRs were categorized into immediate and delayed HSRs based on typical phenotypes. Causative drugs and drug groups were assessed. The prevalence of HSRs were determined, and sex and racial differences were analyzed.

RESULTS: Among 2.7 million patients, 377,474 (13.8%) reported drug-induced HSRs, of which 70.3% were female and 77.5% were white. A total of 580,456 HSRs were reported, of which 53.1% were immediate reaction phenotypes. Common immediate HSRs included hives (48.8%), itching (15.0%) and angioedema (14.1%). Delayed HSR phenotypes (46.9%) were largely rash (99.0%). Pencillins were associated with the most immediate (33.0%) and delayed (39.0%) HSRs. While most HSRs were more prevalent in females and white patients, notable differences were identified for certain rare HSRs including acute interstitial nephritis, which appeared more commonly in males (0.02% vs. 0.01%, p<0.001). Asian patients had more fixed drug eruptions (0.007% vs. 0.002%, p=0.021) and severe cutaneous adverse reactions (0.05% vs. 0.04%, p<0.001).

CONCLUSION: Drug HSRs were reported in 13.8% of patients. Almost one-half of reported immediate HSR phenotypes were hives and almost all reported delayed HSR phenotypes were rash. HSRs largely affected female and white patients, but differences were identified for specific rare HSRs.