Study participants
Individuals with a history of an immediate HSR to a LOCM, who were referred to the Allergy Clinic of Seoul National University Hospital from June 2001 through December 2019, were potential study participants. Those who underwent skin testing after the occurrence of HSR were retrospectively enrolled. The data collected included their age, sex, previous use of LOCM, types of pre-medication, detailed information on every exposure to LOCM, and occurrence of HSR. Data was abstracted from the Contrast Safety Monitoring and Management System (CoSM2oS) in Seoul National University Hospital. Their index HSR was defined as the most recent HSR occurrence prior to the time of the skin test. HSR severity was classified into three categories based on the American College of Radiology’s guidelines on contrast media: mild, moderate, and severe.20 This study was approved by the institutional ethics board of Seoul National University Hospital (IRB No.:1601-002-729) and informed consent was not required due to the retrospective nature of the study.