The following is a summary of “Relationship of Reaction History to Positive Penicillin Skin Tests,” published in the June 2023 issue of Allergy and Clinical Immunology by Kuder et al.

Previous research indicates that up to one-third of patients identified as allergic to penicillin based on positive skin tests have an unclear reaction history. Direct oral challenge (DOC) is advised for patients with a history of low-risk reactions. Diverse published models stratify reaction risk to aid in the application of DOC. The goal is to reevaluate the proportion of penicillin skin test–positive patients with vague or low-risk reaction histories and to evaluate the relationship between the reaction risk history and the probability of positive skin test results. 

Researchers identified patients who were evaluated for penicillin allergy over five years. They documented past drug reactions, demographic variables, skin tests, and challenge outcomes. Patients with positive skin tests were matched with controls with negative skin tests. A risk category was ascribed to drug reaction histories based on two previously published risk stratification models. They utilized logistic regression to determine whether a positive skin test result was associated with a reaction history risk. About 3,382 patients underwent a skin test for penicillin; 207 (6.1%) tested positive. 

Positive skin testing was more common among outpatients (P<.001), younger patients (P<.001), and female patients (P<.001). Each model’s proportions of each risk category were comparable between cases and matched controls. In one stratification model, the likelihood of positive skin tests increased with a history of high-risk reactions. Their data corroborate that a substantial proportion of patients who self-report penicillin allergy and have positive skin test results have a low-risk history, implying that the positive predictive value of penicillin skin testing is low.

Source: sciencedirect.com/science/article/abs/pii/S221321982300291X