Comparison of Acute Phase Thymus and Activation-Regulated Chemokine (TARC) Levels in Food Protein-Induced Enterocolitis Syndrome and IgE-Dependent Food Allergy

Introduction: Patients with food protein-induced enterocolitis syndrome (FPIES) have elevated thymus and activation-regulated chemokine (TARC) levels in the acute phase. However, to the best of our knowledge, no study has evaluated TARC levels in the acute phase of immunoglobulin E-dependent food allergy (IgE-FA). If TARC elevation is a specific response to FPIES among FAs, TARC measurement may help distinguish between FPIES and IgE-FA. Thus, we investigated acute phase TARC levels in patients with FPIES and IgE-FA. Methods: Thirty-one episodes in 16 patients with FPIES and 20 episodes (13 were anaphylaxis) in 20 patients with IgE-FA were included. Patients with eczema were excluded. Serum TARC levels within 6h of allergic reaction onset and age-adjusted TARC ratios (TARC levels divided by age-specific normal TARC values) were compared between the groups. Results: The median age was 1.1 and 3.6 years in the FPIES and IgE-FA groups, respectively (P<0.001). The median (range) serum TARC (pg/mL) levels were significantly higher in the FPIES group than in the IgE-FA group [1,283 (410-3,821) versus 377 (109-1,539); P<0.001]. The median (range) age-adjusted TARC ratios were also significantly higher in the FPIES group [2.56 (0.57-7.86) versus 1.08 (0.15-2.17); P<0.001]. The area under the curve (AUC) for TARC to distinguish FPIES from IgE-FA was 0.926, and the AUC for the age-adjusted TARC ratio was 0.850. The odds ratio for FPIES diagnosis per 1,000pg/mL increase in TARC was 31.6 (P=0.002), and the odds ratio adjusted by age was 17.1 (P=0.016). Conclusion: Acute phase TARC levels were higher in patients with FPIES than in patients with IgE-FA. The increase in acute phase TARC levels was considered to be a specific response to FPIES among FAs. Measurement of TARC levels in the acute phase may help differentiate FPIES from IgE-FA.