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

Background: 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.

Objective: To describe the incidence, manifestations, and outcome of drug allergy in hospitalized patients.

Methods: 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.

Results: 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.

Conclusions: 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.