Further observations of stopping venom immunotherapy: Comparison of patients stopped because of a fall in serum venom-specific IgE to insignificant levels with patients stopped prematurely by self-choice

Abstract

This study extends our experience applying the criterion of a fall in serum venom-specific IgE (RAST) to insignificant levels as an indication to stop venom immunotherapy (VIT) and compares the follow-up results with the results of re-stings in patients who stopped VIT “prematurely” by self-choice. All patients in both groups had a history of venom anaphylaxis, most with cardiovascular and/ or respiratory symptoms and initial elevated serum venom-specific IgE; all patients received VIT. The groups were closely matched for age, sex, nature of initial sting reaction, and insect identification. In the group with low-level RAST titers, the duration of VIT was 6 months to 5 years (mean 2 1 2 years). Re-stings occurred from 1 month to 7 years (mean 2.2 years) after cessation of therapy. There were 75 re-stings in 41 patients with four systemic reactions (10% per patient and 5% per sting). All four reacting patients had tolerated several stings during cessation of VIT before the re-sting systemic reaction; two patients had subsequent stings with no reaction. In the group of patients who stopped VIT for other reasons, the duration of VIT was 5 months to 4 years (mean 1.8 years). Re-stings occurred from 4 months to 6 years (mean 2.1 years) after stopping therapy. There were 74 re-stings in 38 patients with seven systemic reactions in four patients (9.5% per patient and 10.5% per sting). Two of the reacting patients had tolerated stings before the re-sting reaction. The results suggest that, whereas a fall in RAST titers might be an adequate criterion for stopping VIT, most patients probably tolerated re-stings because of either a beneficial effect of the relatively short duration of immunotherapy or the self-limiting nature of insect sting allergy.