Differences in Thymus and Activation-Regulated Chemokine and Squamous Cell Carcinoma Antigen 2 Levels in Food Protein-Induced Enterocolitis Syndrome and Atopic Dermatitis

Introduction: We previously reported that thymus and activation-regulated chemokine (TARC) levels measured after vomiting are useful predictors of a food protein-induced enterocolitis syndrome (FPIES) diagnosis. However, interpreting TARC levels in patients with eczema is difficult, as the levels are similarly elevated in patients with eczema caused by atopic dermatitis (AD). Therefore, we aimed to investigate whether it is possible to predict whether FPIES or AD is responsible for elevated TARC levels by simultaneously measuring TARC and squamous cell carcinoma antigen 2 (SCCA2), another T-helper type 2 biomarker. Methods: Twenty-one episodes in 11 patients with FPIES (FPIES group) and 42 age-matched patients with AD (AD group) were included in this study. Serum TARC and SCCA2 levels were measured, and those values and relative ratios were compared between groups. Results: The median age was 1.1 years in the FPIES group and 1.6 years in the AD group (p = 0.492). The median (interquartile range [IQR]) serum TARC concentration was significantly higher in the FPIES group than in the AD group (2,486 [1,815-4,097] pg/mL and 1,451 [1,201-1,751] pg/mL, respectively; p = 0.002). The median (IQR) SCCA2 concentration was significantly higher in the AD group than in the FPIES group (1.9 [1.3-2.9] pg/mL and 0.8 [0.6-1.5] pg/mL, respectively; p < 0.001). After matching, the analysis using stratified TARC values revealed no significant difference in TARC values between the FPIES and AD groups; however, the TARC/SCCA2 ratio was significantly higher in the FPIES group. Conclusion: Assessing the relative TARC/SCCA2 ratio may help predict whether elevated TARC levels measured after vomiting are caused by FPIES or AD.