Diagnostic accuracy of Ara h 2 for detecting peanut allergy in children

Background Specific IgE to Ara h 2 is a diagnostic test for peanut allergy which may reduce the need for double-blind placebo-controlled food challenges (DBPCFC); however, guidance for using Ara h 2 in place of DBPCFCs has not been validated. Objective To prospectively evaluate 1) diagnostic accuracy of previously published Ara h 2 cut-off levels to diagnose peanut allergy in children and 2) costs. Methods A consecutive series of 150 children age 3.5 to 18 years was evaluated in secondary and tertiary settings in the Netherlands. sIgE to Ara h 2 was the index test, and oral peanut ingestion was the reference test. Oral peanut ingestion was home or supervised introduction for Ara h 2 <= 0.1, DBPCFC for 0.1-5.0 and open food challenge for >= 5.0. Costs were calculated using financial healthcare data. Results A conclusive reference test was performed in 113 children (75%). Sixty-four children (57%) had peanut allergy, as confirmed by a DBPCFC (27/47) or an open challenge (37/50). Forty-nine children (43%) were considered peanut-tolerant after peanut introduction (19/19), a DBPCFC (20/47) or an open challenge (10/50). Area under the curve for Ara h 2 was 0.94 (95% CI 0.90-0.98). The diagnostic flow chart correctly classified 26/26 (100%; 84-100) of children with Ara h 2 <= 0.1 as peanut-tolerant and 34/35 (97%; 83-100) of children with Ara h 2 >= 5.0 as peanut-allergic. At a cut-off of <= 0.1 and >= 5.0, a sensitivity of respectively 100% (93-100) and 53% (38-67) was observed and a specificity of 53% (38-67) and 98% (87-100). Mean annual costs of the flow chart were estimated as euro320-euro636 per patient lower than following national allergy guidelines. Conclusions In this diagnostic accuracy study, which did not take into account pretest probability, we have validated previously published Ara h 2 cut-off levels which are associated with peanut tolerance and allergy.