Drug allergy in a general hospital: results of a novel prospective inpatient reporting system

Abstract

Drug allergies are unpredictable immunologic adverse effects, usually immunoglobulin E-mediated immediate hypersensitivity or T-cell-mediated delayed hypersensitivity. There is a paucity of accurate prospective data on drug allergy in hospitalized patients. To describe the incidence, manifestations, and outcome of drug allergy in hospitalized patients. All newly developed cases, confirmed or suspected, of drug allergy in inpatients using a network-based electronic notification system. Each notification was evaluated by an allergist-immunologist during the same admission. From December 1, 1997 to December 31, 1999, 366 cases were reported from a total of 90,910 admissions. After review, only 210 cases were verified to have drug allergy. Antimicrobials and anti-epileptic drugs comprised 75% of the drug allergies reported. Cutaneous eruptions were the most common clinical presentation (95.7%), with maculopapular rash being the most common morphology. Systemic manifestations occurred in 30%, of which hepatitis was the most common. Serious adverse reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis, and generalized exfoliative dermatitis occurred in 11 (5.2%) patients. There was no case of anaphylaxis attributable to drug allergy. After adjusting for underreporting, the incidence of drug allergy in our hospitalized patients was 4.20 per 1,000 (95% confidence interval [CI] 2.93 to 5.46), drug allergy developing during the course of inpatient treatment 2.07 per 1,000 (95% CI 1.45 to 2.69), and mortality attributable to drug allergy 0.09 per 1,000 (95% CI 0.06 to 0.12) hospitalizations. A network-based, allergist-immunologist-verified, surveillance system enables more accurate labeling of drug allergy. The incidence of drug allergy and mortality in hospitalized patients is low.