English abstract
Objectives: To determine the range of serum IgE in healthy subjects and in asthmatic patients in Oman and to assess the degree of atopy in the asthmatic patients. Method: Serum IgE and in vivo (the skin prick test) and in vitro (the ImmunoCAP test) allergen- specific IgE levels were measured in 44 patients with asthma. Control groups were 19 healthy subjects and 27 asymptomatic allergic subjects. Results: The normal range for serum IgE in the Omani population was established at ≥ 101 IU/ml. The geometric mean (and 95% confidence interval) for asthmatic patients was 468 IU/ml (323–676). Positive results for allergen-specific IgE, defined as responses to ≥ 1 allergen mix in the ImmunoCAP and to ≥ 3 allergens in the skin prick test, occurred in 26/35 (74%) and in 34/44(77%) asthmatic patients respectively. Six out of 38 patients with serum IgE ≥ 101 IU/ml and 2/6 with levels <101 IU/ml gave negative and positive results respectively in the skin prick test. Overall, the degree of reactivity in the skin prick test correlated with the level of total serum IgE (r= 0.54, p<0.001). A similar correlation could not be established with ImmunoCAP reactivity, but sIgE levels ≥ 101 IU/ml were supported by a high frequency of positive ImmunoCAP responses for the majority of allergen mixes. Conclusions: Total serum IgE levels should be routinely monitored in asthmatic subjects as this may give an indication of atopy where skin prick testing is not indicated. Since in a minority of patients serum IgE levels and skin prick results do not predict in the same direction, all laboratory data should be interpreted in context of clinical history.
