Penicillin allergy labels among hospitalized adults: Clinical characteristics and risk stratification using PEN-FAST

Background: Penicillin allergy labels (PALs) are common and are associated with the use of alternative antibiotics, increased healthcare costs, and poorer clinical outcomes. Data on the prevalence and characteristics of PALs among hospitalized patients in Latin America remain limited. Objective: The study aimed to determine the prevalence of PALs and stratify the risk of true penicillin allergy among hospitalized adults. Methods: Data were collected through direct patient interviews and medical record review. Among patients with a PAL, the PAL was obtained by patient self-report; characteristics of the reported allergic reaction were recorded, and risk was assessed using the PEN-FAST clinical decision rule. Multivariable logistic regression was performed to identify factors associated with a PAL. Results: Among 872 patients, 65 had a PAL (7.5%; 95% confidence interval, 5.8%–9.5%). Of these, 21.5% reported a reaction within the previous 5 years, 26.2% had a history of angioedema or anaphylaxis, no severe cutaneous adverse reactions were identified, and 21.5% required medical attention. Most patients were classified as very low/low risk (89.2%), whereas only 4.6% were categorized as high risk. Female sex (adjusted odds ratio [aOR], 2.25; P = 0.004), age ≥50 years (aOR, 1.90; P = 0.019), hypothyroidism (aOR, 3.75; P = 0.006), and antibiotic use within the previous 3 months (aOR, 1.82; P = 0.032) were associated with a PAL. Conclusion: Fewer than 10% of hospitalized adults carried a PAL, and nearly 90% were classified as very low or low risk, suggesting that many may be candidates for penicillin allergy evaluation and potential delabeling.