Hypersensitivity reactions and contrast medium injection: Are they always related?

Preventing post-contrast acute kidney injury and hypersensitivity reactions: UK national audit

AIM

To audit UK radiology departmental protocols related to the prevention of Iodine-based contrast media (ICM) adverse drug reactions (ADRs) and to assess their compliance with the Royal College of Radiologists (RCR) endorsed Royal Australian and New Zealand College of Radiologists' 2018 Iodinated Contrast Guidelines.

MATERIALS AND METHODS

Questionnaires were sent to all UK acute National Health Service (NHS) providers treating adult patients with an audit lead registered with the RCR (162 providers encompassing 211 hospital radiology departments). The questionnaire included three main sections: renal function screening, renal protection regimens, and hypersensitivity reactions prevention and follow-up. Data collection was conducted between April and July 2022.

RESULTS

Sixty-one per cent (129/211) of departments responded, representing 67% of eligible providers. An independent imaging services provider supplied one additional set of data (n=130 overall). Of the responding departments, for post-contrast acute kidney injury (PC-AKI), 41% and 56% had the recommended risk assessment for inpatients and outpatients, respectively. Renal function testing was often over-utilised, and their results were applied improperly. Sixty-eight per cent of departments used the advised threshold for considering renal protection. For hypersensitivity reactions, 9% of departments had the correct risk assessment. Thirty-six per cent of departments had the correct risk mitigation protocol for identified high-risk patients. The documentation and follow-up for hypersensitivity reactions were similarly inadequate.

CONCLUSION

Local protocols on preventing ICM ADRs were largely non-compliant with RCR guidelines. Departments need to update their protocols in line with current evidence to avoid iatrogenic morbidity or unnecessary tests and over-precaution.

Practice parameters for diagnosing and managing iodinated contrast media hypersensitivity

Immediate and nonimmediate hypersensitivity reactions to iodinated contrast media (ICM) have been reported to occur in a frequency of about 0.5%-3% of patients receiving nonionic ICM. The diagnosis and management of these patients vary among guidelines published by various national and international scientific societies, with recommendations ranging from avoidance or premedication to drug provocation test. This position paper aims to give recommendations for the management of patients with ICM hypersensitivity reactions and analyze controversies in this area. Skin tests are recommended as the initial step for diagnosing patients with immediate and nonimmediate hypersensitivity reactions; besides, they may also help guide on tolerability of alternatives. Re-exposition or drug provocation test should only be done with skin test-negative ICMs. The decision for performing either re-exposition or drug provocation test needs to be taken based on a risk-benefit analysis. The role of in vitro tests for diagnosis and pretreatment for preventing reactions remains controversial.

Risk factors for adverse reactions from contrast agents for computed tomography

Background

Symptoms of an adverse reaction to contrast agents for computed tomography are diverse ranging, and sometimes serious. The goal of this study is to create a scoring rule to predict adverse reactions to contrast agents used in computed tomography.

Methods

This was a retrospective cohort study of all adult patients undergoing contrast enhanced CT scan for 7 years. The subjects were randomly divided into either a derivation or validation group. Baseline data and clinically relevant factors were collected from the electronic chart. Primary outcome was any acute adverse reactions to contrast media, observed for during 24 hours after administration. All potential candidate predictors were included in a forward stepwise logistic regression model. Prediction scores were assigned based on β coefficient. A receiver operating characteristic (ROC) curve was drawn, and the area under the curve (AUC) and incidence of acute adverse reactions at each point were obtained. The same process was performed in the validation group.

Results

36,472 patients underwent enhanced CT imaging: 20,000 patients in the derivation group and 16,472 in the validation group. A total of 409 (2.0%, 95% CI:1.9-2.3) and 347 (2.1%, 95% CI:1.9-2.3) acute adverse reactions were seen in the derivation and validation groups. Logistic regression analysis revealed that prior adverse reaction to contrast agents, urticaria, an allergic history to drugs other than contrast agents, contrast agent concentration >70%, age <50 years, and total contrast agent dose >65 g were significant predictors of an acute adverse reaction. AUC was 0.70 (95% CI:0.67-0.73) and 0.67 (95% CI:0.64-0.70) in the derivation and validation groups.

Conclusions

We suggest a prediction model consisting of six predictors for acute adverse reactions to contrast agents used in CT.