It is currently recommended that venom immunotherapy (VIT) be continued as long as the sensitivity persists (indicated by positive venom skin tests or RAST). In this pilot study, we performed a retrospective survey of the clinical and immunologic effects of stopping VIT. The 82 patients studied had received maintenance VIT for a mean of 14 months and had stopped VIT a mean of 43 months before evaluation. Subsequent "field" stings in 28 patients caused systemic reactions in six cases (22%), which is significantly higher than the 1% to 3% systemic reaction rate in patients who remain on maintenance VIT. The 22% reaction rate is a minimal estimate caused by loss of venom sensitivity in some patients and residual venom-specific IgG antibody levels in others. Reevaluation of venom skin tests and IgG levels was possible in 43 patients. A tenfold decline from before VIT skin test results was observed in 27 patients (63%). Skin tests remained clearly positive in 32/43 (74%), became weakly positive in 9/43 (21%), and 2/43 (5%) became negative. The IgG level declined from typical maintenance levels before stopping VIT (mean 7.2 ± 1.2 μg/ml) to levels typical of untreated patients at the time of retesting (mean 1.95 ± 0.3 μg/ml). Despite the marked fall of IgG antibody, one third of the patients still had levels in the average range observed in patients receiving maintenance VIT. We conclude that there is a substantial risk of anaphylactic sting reaction if VIT is stopped while venom sensitivity persists.
ASJC Scopus subject areas
- Immunology and Allergy