Of all forms of specific allergen immunotherapy, the most spectacularly successful appears to be venom immunotherapy (VIT). Placebo-controlled studies using deliberate prospectively observed stings as the primary outcome attest to the value of VIT for protecting subjects with a history of immediate generalized allergic reactions (IGR) [1, 2]. Why then are there so many questions regarding application of this potent immunomodulatory therapy? In contrast to the situation with aeroallergens where exposure is ongoing and thus clinical sensitivity is relatively easy to assess, insect venom exposure is intermittent and erratic. Our major problem relates to assessment of risk of a systemic reaction and death with future stings. A combination of diagnostic laboratory and intradermal venom skin tests for venom-specific IgE (slgE) and clinical criteria have reasonable sensitivity but very limited positive predictive value [3, 4]. The development of slgE is common after stings but only a small proportion of these subjects will have clinical reactivity to stings [3]. Even with a history of IGR and a positive test for slgE the risk of a reaction on future sting by the same insect ranges from approximately 25% to just over 70% depending on severity of previous reaction and the insect involved [2, 3, 5]. These risks are lower if there is a history of less severe reactions but we and others have clearly demonstrated the potential for life-threatening reactions even if previous reactions have been of only moderate severity [2].
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