RISK OF INSECT STING ANAPHYLAXIS AFTER DISCONTINUING VENOM IMMUNOTHERAPY

毒液免疫疗法将对昆虫叮咬产生全身过敏反应的风险从治疗前的50%降低到维持治疗时的不到2%。当治疗在5年或更长时间后停止时，我们以前报道过，在停止治疗后的最初几年，刺痛反应的风险仍低于10%。一些研究者研究了仅在3年后停止治疗，但提出了限制条件，如患者较年轻、反应较轻、治疗期间刺痛挑战阴性或RAST阴性。在治疗的前三年，我们的结果显示，毒液皮肤试验和IgE患者对挑战蜇伤有全身反应，症状轻微甚至微不足道。大多数关于停止毒液免疫治疗的研究报告了仅在停止后的第一年或两年内蜇伤的结果。没有关于患者停止治疗的长期结果的报告。我们假设，在5年后停止治疗的患者，随着时间的推移，敏感性消失，几乎没有反应的风险。然而，最近的报告表明，这种风险可能持续存在，治疗前反应的严重程度可能是反应风险的决定因素。有理由认为，如果毒液皮肤乳头或RAST变为阴性，则可以停止治疗，这种情况发生在少数患者中。然而，皮肤试验对膜翅虫毒液的敏感性水平（可用的最佳指标）与蜇伤临床反应的严重程度无关，并且没有发现任何标志物比病史和皮肤试验预测的平均50%的风险更准确地预测蜇伤的结果。这项研究的结果将显示患者是否可以安全地在3年后停止治疗，而不是我们目前推荐的5-6年，以及在停止治疗后的10年内，不良反应的风险是否仍然可以接受的低。我们还将确定治疗前反应史较轻的患者或皮肤试验和/或RAST阴性的患者是否存在较低的风险。迄今为止，我们已经审查了236例患者，其中32例在1998年季节完成了刺痛挑战（另外7例在1997年之前被叮过）。未发生全身反应。在1999年季节，已联系了更多患者进行刺痛挑战。我们也在寻求更安全的替代方案，以停止VIT患者可能更喜欢或需要维持终身VIT。我们已经开始研究延长12-16周的维持间隔，这可以减少对患者的不便和这种治疗的长期成本。

Venom immunotherapy reduces the risk of a systemic allergic reaction to an insect sting from the 50% level observed before treatment to less than 2% on maintenance therapy. When therapy is discontinued after 5 years or more, we have previously reported that the risk of a sting reaction remains less than 10% in the first few years after stopping treatment. Some investigators have studied discontinuation of therapy after only 3 years, but have suggested restrictions such as younger patients, milder reactions, negative sting challenge during therapy or negative RAST. In the first three years off therapy, our results showed that the venom skin test and IgE patients who did have systemic reactions to challenge stings had mild or even trivial symptoms. Most of the studies of discontinuing venom immunotherapy have reported the outcome of stings only in the first year or two after stopping. There are no reports of the long-term outcome in patients who remain off treatment. We hypothesized that there would become almost no risk of reaction with the disappearance of sensitivity over time in patients who stop treatment after 5 years. However, recent reports suggest that the risk may persist and that the severity of the pre-treatment reaction may be a determinant of the risk of reaction. It has been reasonably assumed that treatment can be stopped if the venom skin teat or RAST becomes negative, which occurs in a minority of patients. However, the level of skin test sensitivity to Hymenoptera venom, the best available indicator, does not correlate with the severity of the clinical reaction to a sting and no markers have been found to predict the outcome of a sting any more accurately than the average 50% risk predicted by history and skin test. The results of this study will show whether patients can safely stop after only 3 years instead of our current recommendation of 5-6 years, and whether the risk of reaction remains acceptably low in the 10 years after stopping therapy. We will also determine whether there is a lower risk in those patients with a less severe history of reaction before treatment or in those who have developed negative skin tests and/or RAST. We have reviewed 236 pateints to date, of whom 32 compeleted sting challenge during the 1998 season (another 7 were previously stung in 1997). No systemic reactions have occurred. Additional patients have been contacted for sting challenge in the 1999 season. We are also seeking safer alternatives to discontinuing VIT for patients who may prefer or require maintenance VIT for life. We have begun studies of prolonged maintenance intervals of 12-16 weeks which could reduce the inconvenience to the patients and the long-term costs of this therapy.