Longitudinal observations of serum IgE and skin prick test response.

The objective of the study was to assess skin prick test and IgE changes in a working population surveyed 5 yr apart and to determine whether age and smoking habits modify these changes. SPTs were performed on 223 subjects by the same method and common allergens (a mixture of grass pollens and a mixture of 95% house dust and 5% house dust mite). IgE measurements were done in duplicate by the same technique at each survey. A SPT-positive response at the first survey was highly predictive of a positive value at the second survey. The prevalence of positive SPT significantly increased in 5 yr (from 17.5 to 24.7%). A strong correlation was observed between IgE levels 5 yr apart (r = 0.92), and the IgE level appeared very stable. The initial IgE level was significantly greater among the converters than in consistently negative subjects (92.3 versus 30.1 IU/ml). Conversely, the initial IgE level was lower for the reverters than in consistently positive subjects (36.8 versus 97.0 IU/ml). In SPT negatives, non- and exsmokers had a greater decrease in IgE than current smokers (p = 0.06). IgE level appears to be a good predictor of SPT changes for both conversion and reversion. The IgE level appears very stable in midadulthood, which suggests that the adult environment may play a small effect in IgE level.