A dot immunobinding assay for penicillin specific antibodies: allergic diagnosis and prediction.

A dot immunobinding assay was used to determine benzylpenicillin (BPO) specific IgE and IgG antibodies. Sera from 39 patients who had a positive history of penicillin allergy and the same number of sera from normal donors without penicillin-allergic history were assessed. The results showed that the mean value of BPO-specific IgE in the group of patients was 3.6 ng/ml while in the group of normal donors it was 0.38 ng/ml. BPO-specific IgE values of 35 samples in the group of patients were greater than 2 ng/ml. In contrast, only one sample in the group of normal donors amounted to 2 ng/ml. Thus 2 ng/ml was arbitrarily chosen to discriminate between normal and patients' sera. Based on this assumption the positive rate is 89.7 percent; the false positive rate would only be 2.6 percent. Furthermore, in the group of patients, the mean value of BPO-specific IgG was 49.1 ng/ml, while in the group of normal donors it was 7.4 ng/ml. However, due to the large variability of serum IgG levels it was not possible to determine a BPO-specific IgG concentration useful for diagnosis or prediction of penicillin allergy.