Oral Food Challenge to Support the Fish Allergenicity Ladder
Based on the pattern of self-reported reaction and distribution of sIgE levels to different fishes (reactivities) and their positive correlation, we proposed that the analyzed fishes presented a ladder of allergenicity difference, from step 1 of the least allergenic fishes (tuna, halibut, salmon), steps 2 (cod) and 3 (herring and grouper) of moderately allergenic fishes to step 4 of highly allergenic fishes (catfish, grass carp and tilapia) (Fig 2). In an attempt to validate such a ladder, we analyzed results from 58 subjects who underwent DBPCFC with both salmon and grass carp. 48/58 (82.8%) subjects failed grass carp DBPCFC while only 19/58 (32.8%) failed salmon DBPCFC (Table S1). Among the 48 subjects who failed grass carp DBPCFC, 60.4% tolerated salmon. No salmon-tolerant subjects reacted to grass carp. ED10 (dose at which an allergic reaction would be elicited in 10% of the population in oral food challenge) was also remarkably higher for the salmon challenge at 10.7g (fish meat, 95%CI 0 – 18.6g) compared to grass carp at only 0.66g (95%CI 0 - 1.04g). On the other hand, we also selected nine subjects, three each from fish-tolerant (no reaction to both fishes), partially tolerant (tolerated salmon but reacted to grass carp) and fish-allergic (reacted to both fishes) groups to undergo open challenge with grouper (Table S1). None of the fish-tolerant subjects reacted to grouper, while all subjects in the partial tolerant and allergic groups failed grouper challenge. Although no remarkable difference in oFASS (i.e. severity of allergic symptoms) was detected, it is noted that 4/6 patients reacted at lower doses of grass carp but higher doses of grouper (mean eliciting doses at 24.3g and 32.0g fish meat, respectively), although the difference did not reach statistical significance with a small cohort size. These results further support the clinical need and relevance of the fish allergenicity ladder.