Relationship between Lower Dose and Injection Speed of Iodinated Contrast Material for CT and Acute Hypersensitivity Reactions: An Observational Study

Background: There are few data on the relationship between acute hypersensitivity reactions and the dose and injection rate of iodinated contrast material for CT. Purpose: To determine the relationship between lower dose and injection speed of iodinated contrast material for CT and the rate of acute hypersensitivity reactions. Materials and Methods: This retrospective study included adults (age >= 18 years) undergoing nonionic iodinated contrast material-enhanced abdominal CT between August 2016 and January 2017 (control period) and between August 2017 and January 2018 (intervention period); all examinations were conducted in an outpatient setting. Compared with CT during the control period, CT during the intervention period involved a reduced dose of contrast material achieved by lowering the CT tube voltage. CT examinations in the control period were performed with 120 kVp, a contrast material dose of 2 mL/kg (maximum, 150 mL), and an injection speed of 3 or 4 mL/sec. CT examinations in the intervention period were performed with 100 kVp, a contrast material dose of 1.5 mL/kg (maximum, 130 mL), and an injection speed of 2.5 or 3 mL/sec. Per-examination rates of acute hypersensitivity reactions to iodinated contrast material were compared between the control and intervention periods with use of a multivariable Poisson regression model, the parameters of which were estimated by using generalized estimating equations with an independence correlation structure. Results: A total of 21947 adults (mean age +/- standard deviation, 59 years +/- 12; 8797 women [40%]) underwent 25119 CT examinations during the control period; 23019 adults (mean age, 59 years +/- 12; 9538 women [41%]) underwent 26491 CT examinations during the intervention period. The rate of acute hypersensitivity reactions was 1.42% (376 of 26491 examinations; 95% confidence interval [CI]: 1.28%, 1.57%) in the intervention period and 1.86% (468 of 25119 examinations; 95% CI: 1.70%, 2.04%) in the control period, with a multivariable-adjusted relative risk of 0.85 (95% CI: 0.74, 0.99; P = .03). Conclusion: Reduction in the dose and injection speed of iodinated contrast material for CT was associated with a lower rate of acute hypersensitivity reactions to iodinated contrast material. (C) RSNA, 2019