The impact of a drug allergy label in an internal medicine ward

Background. Drug hypersensitivity reactions are presumably immune-mediated reactions that cause reproducible signs and/or symptoms. Overdiagnosis of drug allergy, frequently self-reported, is common and carries significant limitations. We intended to analyze the frequency and impact of drug allergy in hospitalized patients. Methods. A retrospective study was conducted in an Internal Medicine ward at a tertiary hospital in Portugal. All patients with a drug allergy report admitted within a 3-year period were included. Data were collected from their electronic medical records. Results. We found that 15.4% of patients had a report of drug allergy, with antibiotics being the most common (56.4%), followed by non-steroidal anti-inflammatory drugs (21.7%) and radiocontrast media (7.0%). The allergy report affected the clinical approach of 14.5% of patients by motivating the use of second-line agents, or the eviction of necessary procedures. The usage of alternative antibiotics entailed a cost increase of 2.4 times. There were 14.7% of patients to whom the suspected drug was administered: 87.0% tolerated and 13.0% developed a reaction. Only 1.9% were referred to our Allergy and Clinical Immunology department and proceeded in their allergy study. Conclusions. In this study, a considerable number of patients had a drug allergy label on their records. This label contributed to an increase in the cost of treatment, or the avoidance of necessary exams. However, disregarding an allergy record may lead to potentially life-threatening reactions that proper risk assessment could avoid. Further investigation should always be part of the follow-up routine of these patients, and better articulation between departments should be encouraged.