Background: Post-emetic elevation in thymus and activation-regulated chemokine (TARC) levels has been reported in patients with food protein-induced enterocolitis syndrome (FPIES); however, no studies have investigated differences in TARC levels between FPIES and other diseases. Objectives: We evaluated the clinical usefulness of TARC measurement in differentiating between FPIES and infectious gastroenteritis. Methods: This study included 8 patients with solid-food FPIES (FPIES group; hen’s egg [n = 6], rice [n = 1], and short-neck clam [n = 1]; a total of 11 episodes necessitating emergency department visit or positive result of oral food challenge test) and 17 patients with infectious gastroenteritis (control group), and all patients had no eczema. Post-emetic serum TARC levels and modified TARC levels (serum TARC value – normal mean for each age) were compared between the 2 groups. Results: The median (range) ages for the FPIES and control groups were 0.7 (0.5–6.2) and 1.8 (0.1–4.4) years, respectively (p > 0.05). In the FPIES and control groups, median (range) TARC levels were 2,911 (1,062–7,816) and 600 (277–2,034) pg/mL, and median (range) modified TARC levels were 2,204 (355–7,109) and 129 (0–1,314), respectively. The TARC and modified TARC levels were significantly higher in the FPIES group than in the control group (p < 0.001 for both). Conclusion: In the absence of eczema, post-emetic serum TARC levels might be a potential diagnostic biomarker for distinguishing FPIES from infectious gastroenteritis.

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