Assessment of peanut allergy in children

The gold standard for the diagnosis of peanut allergy is the oral peanut food challenge (OPFC). However, OPFCs may cause anaphylaxis and could be negatively perceived by patients. Therefore peanut skin prick testing (SPT), serum peanut specific-IgE level or immediate-skin-application-food-testing (I-SAFT) are adjuvants in the diagnosis of peanut allergy. Cut-offs of tests that are predictive of peanut allergy have been proposed but are not thought to predict reaction severity. The relevance of a skin contact reaction with peanut in a peanut sensitised child is unclear. We prospectively determined the validity of reported diagnostic cutoff levels of peanut allergen skin tests and specific-IgE, and the usefulness of combining these. Eighty-four peanut sensitised children were included. Fifty-two of 85 OPFC were positive. SPT specificity was 67% at  8 mm and 100% at  15 mm. Combinations of a SPT of  8 mm with a positive I-SAFT and a peanut specific-IgE  0.37 kU/L were 88% specific and 38% sensitive. Thus combining available allergy tests does not improve their clinical usefulness. Previously described diagnostic cutoff levels do not have general applicability. Next we determined the frequency and significance of contact sensitivity to peanut in peanut sensitised children. I-SAFTs were performed with one gram of peanut butter in 281 peanut sensitised children and 41% were positive. No systemic reactions occurred following topical application of peanut butter. I-SAFT sensitivity and specificity was 50% and 82% respectively. Systemic reactions following peanut butter skin contact appear unlikely.The third study determined the usefulness of allergy tests for predicting the risk of anaphylaxis on challenge. Peanut sensitised children who completed open-label OPFCs were included. The challenge protocol provided for challenges to be continued beyond initial mild reactions. There were 34 in the control group and 21 who developed anaphylaxis. The mean peanut SPT size and specific-IgE level was associated with reaction severity on challenge. Therefore available tests for peanut allergy assist in predicting the risk of anaphylaxis during challenge in peanut sensitised children.Finally we investigated parental satisfaction with OPFC. Telephone interviews were conducted with parents whose children had undergone OPFC. Forty-six participated and 54% were very satisfied with the OPFC experience. When the challenge was perceived as equivocal parental satisfaction was lower. Recall of the amount of peanut ingested, outcome and management advice was poor. Comprehensive education and follow-up after OPFC is required especially when the challenge outcome is inconclusive