Should patients with risk factors be tested for hypersensitivity to contrast media: a prospective study

Bridging the gap between bench and clinic: the importance of understanding the mechanism of iodinated contrast media hypersensitivity

Since the advent of CT, iodinated contract media (ICM) has become one of the most regularly administered intravenous medications in clinical settings. Although considered generally safe, ICM is one of the most common causes of adverse drug reactions in clinical practice, accounting for more than 2 million adverse reactions worldwide. Currently, there are few useful tools to diagnose patient hypersensitivity, with the major limitation being the lack of consensus regarding the mechanisms of hypersensitivity to ICM. While there is an overwhelming abundance of literature pertaining to clinical features including incidence, symptomatology, and risk, few studies have further investigated the underlying mechanisms behind their clinical observations. Of the available literature discussing pathophysiology, most primary studies were completed over 20 years ago, since which the molecular characteristics of ICM have changed. Furthermore, many reviews mentioning pathophysiology fail to adequately emphasize the clinical importance of understanding the molecular pathways involved in hypersensitivity. In this review, we aim to emphasize the clinical relevance of pathophysiology as it relates to the prediction and diagnosis of hypersensitivity reactions to ICM. To this end, we will first briefly characterize hypersensitivity reactions to ICM with respect to epidemiology and clinical presentation. We will then present the existing evidence supporting various proposed mechanisms of hypersensitivity, highlighting the gaps that remain in the mechanistic delineation of both immediate and delayed reactions. Finally, we discuss the possibility of in vitro testing as a way to predict and diagnose hypersensitivity reactions, pending a more complete elucidation of mechanisms.

Outcomes in patients with known contrast allergy undergoing contrast-enhanced endourological procedures: a retrospective cohort study

BACKGROUND

Intravenous administration of iodinated contrast agents carries the risk of allergic reaction, yet this risk is unclear with administration into the urinary tract. We sought to evaluate patients with known contrast, iodine, or shellfish allergies for allergic response when undergoing urologic imaging requiring intraluminal, urinary tract contrast administration.

MATERIALS AND METHODS

We retrospectively reviewed consecutive patients undergoing endourologic procedures from 2010 to 2015 at our institution. Clinical records were reviewed for demographics, medical history, allergies, procedure details, fluids administered, anesthetic and pharmacologic agents administered, and continuous monitoring parameters. Patients with known allergies to iodine, shellfish, and/or contrast were identified and evaluated for clinical or hemodynamic signs of allergy. A convenience sample of 50 patients without allergy history was used as a comparison group.

RESULTS

We identified 1,405 procedures involving 1,000 consecutive patients. Procedures included retrograde pyelograms and antegrade nephrostograms. Eighty-six cases involving 58 patients with contrast, iodine, or shellfish allergies were identified. Of those with contrast allergy history, 18 (20.1%) cases involved patients with a history of anaphylactic reaction. Of these, 11 (61%) received steroid prophylaxis. No patients in either group (Allergy, No Allergy) were identified as having an allergic reaction during the procedure. There were no statistically significant differences in intraoperative intravenous fluids (p=0.931), procedure duration (p=0.747), or vasopressor use (p=0.973) between groups. Due to the zero event rate of contrast allergy, we used the Hanley and Lippman-Hand method, which places true population risk (95% confidence interval) of a significant event at less than 3.5%.

CONCLUSIONS

In 86 cases involving patients with a history of contrast allergy, we found no evidence of clinically significant allergic reaction to intraluminal endourologic contrast administration under continuous anesthesia monitoring. The risk of significant reactions to contrast administered within the urinary tract appears to be low in these patients, regardless of prophylaxis.

Assessment of immediate and non-immediate hypersensitivity contrast reactions by skin tests and provocation tests: A review

INTRODUCTION

Allergic and nonallergic hypersensitivity reactions to iodinated contrast media (ICM) and gadolinium-based contrast media are classified as immediate or non-immediate hypersensitivity reactions (IHR and NIHR), respectively. Skin tests and provocation tests are recommended for the evaluation of hypersensitivity reactions to contrast agents; however provocations are not common in clinical practice.

METHODS

A MEDLINE search was conducted to investigate studies comprising both skin tests and provocation tests that evaluated hypersensitivity reactions to ICM.

RESULTS

Nineteen studies were identified that reported on skin tests, followed by provocations. In the case of IHR to ICM, 65/69 (94%) patients with a positive skin test for the culprit media tolerated a challenge with a skin-test-negative alternative ICM. In IHR to ICM with a negative skin test for the culprit media, provocations were positive in 3.2%-9.1% patients. In the case of a NIHR to ICM with a positive skin test, provocation with a skin-test-negative agent was tolerated in 75/105 (71%) of cases. In NIHR with a negative skin test for the culprit agent, re-exposure to the culprit or an alternative was positive in 0%-34.6% patients. Provocations with the same ICM in skin test positive patients with IHR or NIHR were positive for a majority of the patients, although such provocation tests were rarely performed. Data on hypersensitivity reactions, skin tests and provocations with gadolinium-based contrast media were limited; however, they exhibited a pattern similar to that observed in ICM.

CONCLUSION

In both ICM and gadolinium-based contrast media, the risk of an immediate repeat reaction is low when skin tests are negative. In contrast, a provocation with a skin-test-positive contrast medium showed a high risk of an immediate repeat hypersensitivity reaction. Therefore, a thorough medical history is necessary, followed by skin tests. A provocation is recommended, for diagnostic work-up, when the diagnosis is uncertain.

SIRM-SIAAIC consensus, an Italian document on management of patients at risk of hypersensitivity reactions to contrast media

Hypersensitivity reactions (HRs) to contrast media (CM) can be distinguished in immune-mediated (including allergic reactions) and non-immune-mediated reactions, even if clinical manifestations could be similar. Such manifestations range from mild skin eruptions to severe anaphylaxis, making it important for radiologists to know how to identify and manage them. A panel of experts from the Società Italiana di Radiologia Medica e Interventistica (SIRM) and the Società Italiana di Allergologia, Asma e Immunologia Clinica (SIAAIC) provided a consensus document on the management of patients who must undergo radiological investigations with CM. Consensus topics included: the risk stratification of patients, the identification of the culprit CM and of a safe alternative by an allergy workup, as well as the use of premedication and the correct procedure to safely perform an elective (i.e., scheduled) or urgent examination. The most important recommendations are: (1) in all patients, a thorough medical history must be taken by the prescribing physician and/or the radiologist to identify at-risk patients; (2) in patients with hypersensitivity reactions to CM, the radiologist must consider an alternative, non-contrast imaging study with a comparable diagnostic value, or prescribe a different investigation with another class of CM; (3) if such options are not feasible, the radiologist must address at-risk patients to a reference centre for an allergy evaluation; (4) if timely referral to an allergist is not viable, it is recommended to use a CM other than the responsible one, taking into account cross-reactivity patterns; in the case of patients with histories of severe reactions, the presence of an anesthesiologist is also recommended and a premedication is suggested.

Common allergies do not influence the prevalence of cutaneous hypersensitivity reactions to antiepileptic drugs

OBJECTIVE

The aim of the study was to establish whether the presence of common allergies increases the risk of drug-related hypersensitivity reactions among patients with epilepsy treated with antiepileptic drugs (AEDs).

METHODS

We studied 753 patients with epilepsy seen in tertiary outpatient epilepsy clinic. We obtained data related to epilepsy type, past and ongoing treatment with AEDs, occurrence of maculopapular exanthema or more serious cutaneous adverse reactions (Stevens-Johnson syndrome - SJS) and their characteristics. We noted an occurrence of allergic reactions unrelated to treatment with AED, including rash unrelated to AED, bronchial asthma, persistent or seasonal allergic rhinitis, atopic dermatitis, rash after specific food and other allergic reactions.

RESULTS

There were 61 cases of AED-related cutaneous hypersensitivity reaction (including 3 cases of SJS) noted in association with 2319 exposures to AEDs (2.63%) among 55 out of 753 patients (7.3%). Cutaneous hypersensitivity reaction to AED was most commonly noted after lamotrigine (12.1%), carbamazepine (5.4%) and oxcarbazepine (4.1%). Prevalence of allergic reactions unrelated to AED was similar between patients with and without AED-related cutaneous hypersensitivity reaction (rash unrelated to AED: 16.4% vs. 10.2%; bronchial asthma: 1.8% vs. 0.1%; persistent allergic rhinitis: 7.3% vs. 10.2%; seasonal allergic rhinitis: 7.3% vs. 11.7%; atopic dermatitis: 0 vs. 0.7%; rash after specific food: 5.4% vs. 6.4%; other allergic reactions: 5.4% vs. 5.2%, respectively; P>0.1 for each difference).

CONCLUSIONS

Presence of common allergies is not a significant risk factor for AED-related cutaneous hypersensitivity reaction among patients with epilepsy.

Preventing Allergic Reactions to Gadolinium-Based Contrast Agents

Although the low incidence of immediate-type gadolinium-based contrast agent (GBCA) allergic reactions is widely known, preventing these reactions and properly managing them to reduce their adverse sequel can improve the already exceedingly favorable GBCA safety profile. This review article should help those who order, supervise, or administer GBCA contrast agents, including recognizing and handling allergic reaction risks intrinsic to their use. Areas of focus include factors indicating increased allergic reaction risk, patient selection strategies, skin testing, premedication, and treatment of adverse events.

Pathophysiology of Immediate Reactions to Injectable Gadolinium-based Contrast Agents

OBJECTIVE

The aim of this paper was to review the classification of adverse drug reactions, highlight the known pathophysiology of immediate hypersensitivity reactions, and discuss the utility of diagnostic testing for immunologically mediated immediate reactions to gadolinium-based contrast agents (GBCAs).

METHODS

Current literature on immediate reactions to GBCA was reviewed and summarized.

RESULTS

Adverse drug reactions to GBCA are rare, and can be attributed to physiologic, immunologic, and nonimmunologic processes. When immunologic reaction is suspected, particularly in the case of severe reactions, skin testing may be useful to confirm allergy and identify alternative agents for subsequent studies.

CONCLUSION

As GBCAs are widely used for the diagnosis and monitoring of disease, the incidence of adverse drug reactions to GBCA warrants ongoing development of approaches to diagnosis and avoidance of these adverse events.