Comparison of Diagnostic Tests for Sesame Food Allergy
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
Michael Y Appel, PhD, Michael R Goldberg, MD PhD, Liat Nachshon, MD, Yitzhak Katz, MD FAAAAI
Rationale:   Sesame food allergy (SFA) is prevalent in Israel, with increasing incidence in the US. Oral food challenges (OFC) remain the diagnostic standard for SFA, but are not without risk. Reports on specificity and sensitivity of skin prick tests (SPT) for SFA are highly variable.  

Methods: Thirty patients (ages 2-20 years) with a history of SFA were evaluated by OFC. SPT was performed with a commercially available or a high-concentration (HC-sesame) extract prepared from reduced-fat sesame flour (100mg/ml). Induced CD63 expression after exposure to 1mg/ml sesame protein was assessed in the Basophil activation test (BAT).  Empirical receiver operating characteristic (ROC) analysis was used to determine the critical values for optimized test performance.

Results: Positive OFC was observed in 20/30 patients (eliciting dose range: 15-4000mg, median: 240mg). BAT (CD63%) and HC-sesame SPT (wheal in mm) mean values differed significantly between the OFC positive and OFC negative groups (BAT: 33.5% vs. 1.4%, p<0.0001; HC-sesame SPT: 13.7mm vs. 5mm, p<0.0001 by Student's two-tailed t-test).  ROC analysis of HC-sesame SPT demonstrated at a ≥9mm wheal, a specificity and sensitivity of 80% and 95%, respectively, while a wheal >12mm was 100% specific, with 55% sensitivity.  The commercially available extract at ≥3mm wheal, gave a specificity and sensitivity of 30% and 75%, respectively. For BAT, 100% specificity was reached at >6% CD63 induction, yielding 80% sensitivity. All four OFC positive patients with CD63 levels ≤6% had HC-sesame SPT wheals ≥12mm.

Conclusions: In situations that preclude the administration of OFC, the combination of SPT and BAT may predict clinical reactivity.