Intradermal testing of iodinated contrast media: Should we test up to pure or with diluted compounds only?

BACKGROUND: Intradermal testing (IDT) with iodinated contrast media (ICMs) is an established diagnostic tool in patients with ICM hypersensitivity. Currently, it is unclear which test concentration is the more useful one, up to pure or up to 1:10 diluted ICMs. METHODS: We searched the literature database PubMed for eligible papers dealing with ICM allergy and their IDT results. We analyzed the data presented by the papers and compared the pooled groups tested with diluted and undiluted ICMs. RESULTS: We identified 29 eligible original papers, and extracted data of 1137 patients that formed the study population. Although in the cohort tested with diluted ICMs the number of tested ICMs was greater, the percentage of positive tests was significantly less (9.0% vs. 24.7%; P < 0.0001; OR 0.30 [0.26-0.34]). The frequency of positive tested culprit ICMs was also lesser in the group tested with diluted ICMs (31.0% vs. 72.5%; P < 0.0001; OR 0.17 [0.12-0.23]). The number of drug provocation tests (DPTs) was greater in patients with diluted IDTs (374 vs. 89; P < 0.0001; OR 2.54 [1.93-3.36]). We detected an increased sensitivity in patients with undiluted tests (0.774 vs. 0.282) and a nearly identical specificity in both groups (1 vs. 0.983). CONCLUSIONS: For the first time, we show that IDT up to pure ICM concentrations is superior to using diluted ICMs only. Possibly, we can reduce the number of DPTs when performing IDTs with pure ICMs. In the undiluted group, there were no hints for skin irritations or unspecific test reactions.

Cross-reactivity among iodinated contrast agents: should we be concerned?

BACKGROUND: Although several papers deal with "cross-reactivity" in patients with iodinated contrast medium (ICM) hypersensitivity reactions (HSRs), there is no in-depth knowledge of this phenomenon. To define ICM-groups as potential reaction partners and to identify any potential clinical relevance in patients with ICM-HSRs. METHODS: The literature database PubMed was searched for eligible papers dealing with ICM-allergy and "cross-reactivity". The data presented by the papers was analyzed and individual patient data was extracted for re-evaluation based on a definition for both 'polyvalent reactivity' and 'cross-reactivity' as well as for chemical structure-dependent ICM-groups. RESULTS: Twenty-five original papers (with n=340 extracted patients) formed the study population. Incidences of polyvalent reactivity were non-significantly higher than incidences of cross-reactivity (both range from 0% to 100%). Crossover evaluation in reaction pairings (culprit ICM A with ICM B versus culprit ICM B with ICM A) showed concordance of only 30%. Data support rather non-cross-reactivity (individual reaction pattern) than cross-reactivity constellations. CONCLUSIONS: The obtained results favour an individual reaction pattern, rather than a reactivity driven by chemical structures and so-called cross-reactivity.