The Association Between Risk Stratification Models And The Likelihood of Positive Penicillin Skin Tests

One-third of penicillin skin-test positive (+ST) patients have a vague reaction history (Ann Allergy Asthma Immunol 2000;85:160). Direct oral challenge (DOC) has been recommended for patients with a low-risk reaction history. We analyzed the association between patient-reported penicillin reaction history and +ST. We identified patients who underwent penicillin allergy evaluation from January 2014-December 2018. We recorded drug reaction history, demographic variables, skin testing and DOC results. Matched controls (age/gender/date/testing location) were identified for +ST patients. Drug reaction histories were assigned a risk category (high/moderate/low) based on two risk stratifications (Model 1: Shenoy. JAMA 2019;312:188; Model 2: Blumenthal. JACI Pract 2019;7:2411). We used logistic regression to investigate whether reaction history risk is associated with +ST. Penicillin skin testing was performed in 3,391patients: 215 (6.3%) had +ST; +ST were more frequent in outpatients (p<0.001), younger (p<0.001), and female patients (p<0.001), and were associated with history of requiring treatment (p<0.05) and seeking medical care (p=<0.05) for reaction. Percentages of high/moderate/low risk in each model were similar in cases vs. matched controls: Model 1: 17/62/18 vs. 11/65/23 (p=0.25); Model 2: 3/53/34 vs. 2/48/50 (p=0.67). Likelihood for +ST in cases categorized as high-risk in Model 1 approached statistical significance (p=0.052). Our data confirm a substantial proportion of patients who self-report penicillin allergy and have +ST have a low-risk history. Risk histories (high/moderate/low) in +ST patients do not significantly differ from negative skin test patients. Further studies will be required to reconcile these data with recent reports describing successful DOC without prior skin testing.