ABSTRACT
Used since 1929 in medical practice, nowadays four chemical varieties of intravascular iodine based radiocontrast media (I-RCM) are available: ionic monomers with high osmolarity, ionic dimers with low osmolarity, non-ionic monomers with low osmolarity and non-ionic iso-osmolar dimers. Increasing prescription of l-RCMs augments the number of reported hypersensitivity reactions. I-RCM induced hypersensitivity reactions can be dclasified in two types: immediate hypersensitivity reactions (IHRs - occurring within the first hour) and delayed hypersensitivity reactions (DHRs - occurring between 1 hour and 7 days). IHRs usually present as urticaria and angioedema but may associate severe respiratory and cardiovascular symptoms. Risk factors for an IHRs include a prior immediate reaction, personal history of atopic diseases (mainly asthma) and treatment with beta blocking agents. Diagnostic tests for IHRs include blood tests (serum tryptase) and skin tests (prick and intradermal) performed 2 to 6 months after IHR. High osmolarity of the I-RCM is the factor most strongly associated with IHRs. Primary prevention of IHRs involves the use of non-ionic low-osmolar or iso-osmolar agents for all intravascular procedures. DHRs are usually mild to moderate in severity, transient and self-limiting, presenting as maculopapular rash in more than 50% of cases. As with IHRs, the most important risk factor for DHRs is a previous reaction to I-RCM. Assessment of DHRs includes skin prick tests, intradermal and patch tests. Due to extensive cross-reactivity between I-RCM, a change of product is no guarantee against a repeated reaction. Current premedication procedures in patients with previous severe reactions can reduce symptoms, but may not prevent recurrent reactions.
Subject(s)
Contrast Media/adverse effects , Hypersensitivity, Delayed/chemically induced , Hypersensitivity, Immediate/chemically induced , Iodine/adverse effects , Radiology , Contrast Media/administration & dosage , Humans , Hypersensitivity, Delayed/diagnosis , Hypersensitivity, Immediate/diagnosis , Iodine/administration & dosage , Skin TestsABSTRACT
Allergic Bronchopulmonary Aspergillosis (ABPA) is an uncommon respiratory condition in which Asp. spp spores and mycelia inhalation trigger an immuno allergic inflammatory response in the bronchial airways. ABPA mostly develops in asthmatic and cystic fibrosis patients. The true prevalence of ABPA in not known. It is important to exclude ABPA in all asthmatics with positive skin reactivity to Aspergillus. Currently, a number of allergens from A. fumigatus have been cloned and the mRNA was purified - these are the recombinant antigens which can be used to distinguish between ABPA and fungal sensitization. IgE specific for Asp f 4 and Asp f 6 are restricted to ABPA patients and have a sensitivity and specificity of 90% and 100%, respectively. Aspergillus hipersensitivity can be demonstrated using in vivo (skin prick test) and in vitro methods (specific IgE and IgG, serum precipitins). In ABPA skin prick test is almost always positive. Normal levels of total IgE exclude ABPA. Serum total and specific IgE vary according to disease activity and are usefull for monitoring the treatment.
