Venom Iimmunotherapy Given Every 3 or 4 Months is Effective. A Prospective Comparison with the Conventional Regimen

Background. The standard venom immunotherapy (VIT) involves the administration of the maintenance dose every 4-6 weeks. This regimen may have compliance problem especially in the long term, thus extended intervals have been proposed. Objective. We prospectively compared the efficacy of 3- or 4-month extended maintenance dose vs the conventional regimen. Methods. Patients receiving immunotherapy with a single venom were offered the extended maintenance dose (EMD), and were then followed-up for field re-stings. Only the re-stings by the insect for which the patients received immunotherapy were considered. A matched group of patients receiving the conventional maintenance dose (CMD) was used for comparison, by univariate and multivariate analysis. Results. Seventy-six patients (60 male, mean age 48 years) on EMD were re-stung on 247 occasions by the insect for which they were receiving immunotherapy. The group on CMD, included 110 patients (82 male, mean age 44 years) certainly re-stung on 167 occasions by the specific insect. The rate of re-sting without reaction was 93.5% in the EMD and 81.5% in the CMD group with a significant difference in favour of the former (p= 0.001). At logistic regression analysis only age, but not maintenance dose protocol, was predictive of subsequent systemic reactions. Conclusions. The EMD is as effective and safe as the CMD. The delayed maintenance seems to be the best option in term of convenience and economic savings.