Factors Associated with Acute Allergic-like Reactions to Intravenous Non-ionic Iodinated Contrast Material in a Philippine Tertiary Private Hospital: A Case–Control Study

Background: Non-ionic iodinated contrast media (ICM) are widely used for contrast-enhanced imaging and generally have a favorable safety profile. However, acute allergic-like reactions (AARs) remain a clinical concern. Understanding patient-related risk factors is essential for improving preventive strategies and ensuring safe radiologic practice. Objective: To determine the clinical severity and factors associated with AARs to intravenous non-ionic ICM among patients who underwent contrast-enhanced imaging at the University of Santo Tomas Hospital (USTH). Methods: A retrospective review was conducted on 2,496 patients who received intravenous non-ionic ICM from January 2019 to August 2025. Data were obtained from contrast reaction reports, radiology records and pharmacovigilance databases. Univariable and multivariable logistic regression analyses were performed to identify independent predictors of AAR. Sensitivity analysis was conducted to assess model robustness. Results: A total of 39 cases of AAR were identified within the sampled population. All reactions were mild to moderate, with no severe or life-threatening events reported. Univariable analysis identified allergic rhinitis, drug allergy, other atopy, family history of atopy, prior contrast reaction and use of premedication as significant factors. Multivariable analysis revealed four independent predictors: allergic rhinitis (adjusted OR = 4.85, 95%CI 1.74–13.56), drug allergy (adjusted OR = 4.23, 95%CI 1.99–8.97), other atopy (adjusted OR = 5.16, 95%CI 1.26–21.09) and prior contrast reaction (adjusted OR = 18.06, 95%CI 5.93–54.98). Sensitivity analysis confirmed drug allergy and prior contrast reaction as the most robust predictors. Conclusion: AARs to non-ionic ICM are uncommon and typically mild, supporting the continued safe use of these agents. However, patients with drug allergies or prior contrast reactions were the strongest independent predictors, supporting targeted pre-procedure risk assessment and enhanced monitoring of high-risk patients. Keywords: Radiocontrast; radiology; contrast-enhanced; acute allergic-like reactions; non-ionic iodinated contrast material