Contrast Media Allergy
Conditions
Keywords
IgE, Allergy, Contrast Media, Skin test
Brief summary
The study aims to evaluate the persistence of IgE-mediated allergy to contrast media (CM) after a second exposure in patients who tested positive at both the first and second evaluations for CM allergy. It also aims to analyze the risk factors associated with the persistence of IgE-mediated sensitization after the second allergological assessment.
Detailed description
Drug allergy is often overdiagnosed, as only about 25% of cases labeled as allergic are confirmed. IgE-mediated drug allergy, responsible for immediate reactions up to anaphylaxis, carries inherent risks and relies primarily on in vivo testing, supplemented by in vitro assays in selected cases. In vivo assessment includes skin tests (ST), which, when positive, detect drug-specific IgE bound to mast cells, and drug provocation tests (DPT), which involve controlled re-exposure to the suspected drug. When IgE-mediated allergy is confirmed, drugs with positive ST are strictly contraindicated for life. Drugs with negative ST are generally considered safe, and tolerance is often verified through DPT performed in specialized settings using stepwise dose escalation up to near-therapeutic doses. In some cases, drugs are reintroduced directly in real-life conditions without prior DPT. Contrast media (CM) can trigger systemic reactions even at very low doses. In such cases, in vitro testing should ideally precede DPT to minimize systemic exposure. However, its use is limited by the small number of commercially available drug allergens, the need for specialized expertise for techniques such as the basophil activation test, and variable sensitivity depending on the drug, which remains largely unknown for CM. Skin testing for CM allergy has a very high negative predictive value (\>95%), indicating that most patients with negative ST tolerate subsequent CM exposure. As a result, many centers do not systematically perform DPT after negative ST. Evidence suggests that IgE-mediated drug allergy, including CM allergy, may decline over time, with conversion from positive to negative ST occurring after several years. However, it is unclear whether this reflects a true loss of clinical allergy, as documented re-exposures are rare and mostly anecdotal. Clinical experience shows that allergy may either resolve or persist despite negative follow-up tests. Finally, the severity of drug-induced allergic reactions may be increased in patients with mast cell activation syndrome or mastocytosis, conditions characterized by elevated mast cell burden or reactivity and often suspected in the presence of elevated baseline serum tryptase levels.
Interventions
DIAGNOSTIC_TESTSkin testing
Commercial contrast media will be used to perform skin prick testing or intradermal testing with 0.02-0.05 mL of allergenic solution. If not previously performed, a standard panel of prick tests with environmental allergens will be used to assess atopic status. Positive (histamine 10 mg/mL) and negative (saline) controls will be included. Skin testing will begin with prick tests, starting at the dilution that was positive during the initial evaluation. If negative, testing will proceed with intradermal injections using increasing concentrations until a positive response is observed. Once a positive result is obtained, skin testing for that contrast medium will be discontinued. A prick test will be considered positive if a wheal ≥3 mm with erythema and pruritus appears after 15 minutes. An intradermal test will be considered positive if a wheal ≥3 mm with erythema and pruritus appears after 20 minutes.
OTHERBaseline serum tryptase measurement
Seven milliliters of venous blood will be collected for baseline serum tryptase measurement.
Sponsors
University Hospital, Montpellier
Study design
Observational model
CASE_ONLY
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
\- Adult patients (≥18 years) with confirmed IgE-mediated allergy to contrast media products after a first exposure.
Exclusion criteria
* Patients receiving H1 antihistamines for an allergic condition at the time of evaluation. * Patients with active eczema and/or uncontrolled asthma. * Pregnant or breastfeeding women, or women who have recently given birth. * Individuals under legal protection (e.g., guardianship). * Individuals deprived of liberty or involved in judicial proceedings. * Individuals without health insurance coverage. * Absence of clear, written informed consent.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Prevalence of IgE-mediated allergy to contrast media after the first exposure | Inclusion | A skin prick test is considered positive if, after 15 minutes, a wheal measuring at least 3 mm appears, associated with erythema and pruritus. An intradermal test is considered positive if, after 20 minutes, a wheal measuring at least 3 mm appears, associated with erythema and pruritus |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Risk factors of patients with IgE-mediated hypersensitivity to contrast media | Inclusion | The presence of risk factors will be determined by analyzing the association between data extracted from the Drug Allergy and Hypersensitivity Database (DAHD) (i.e., sociodemographic characteristics, initial reaction to contrast media, results of the first allergy tests, and the presence of other allergic factors) and the persistence of reactivity to contrast media in patients with serum tryptase levels higher than 11 µg/L. |
Countries
France
Contacts
CONTACTDr CHIRIAC
PRINCIPAL_INVESTIGATORDr CHIRIAC
University Hospital, Montpellier
Outcome results
None listed