Can Faecal Zonulin and Calprotectin Levels Be Used in the Diagnosis and Follow-Up in Infants with Milk Protein-Induced Allergic Proctocolitis?

Objective: The aim of our study was to investigate whether a 1-month-long milk-free diet results in a reduction in faecal calprotectin (FC) and faecal-zonulin-related proteins (FZRP) in children with milk-protein-induced allergic proctocolitis (MPIAP).
Materials and Methods: This is a single-centre, prospective, observational cohort study involving 86 infants with MPIAP, aged 1-3 months, and 30 healthy controls of the same age. The FC and FZRP were marked using the ELISA method (IDK ^® Calprotectin or Zonulin ELISA Kit, Immunodiagnostik AG, Bensheim, Germany). The diagnosis of MPIAP was confirmed with an open milk challenge test.
Results: FFC and FZRP proved useful in evaluating MPIAP treatment with a milk-free diet, and the resolution of allergic symptoms and a significant ( p = 0.0000) decrease in the concentrations of both biomarkers were observed after 4 weeks on the diet. The FC and FZRP concentrations were still higher than in the control group. A high variability of FC concentrations was found in all the study groups. An important limitation is the phenomenon of FZRP not being produced in all individuals, affecting one in five infants.
Conclusions: FC and FZRP can be used to monitor the resolution of colitis in infants with MPIAP treated with a milk-free diet, indicating a slower resolution of allergic inflammation than of allergic symptoms. The diagnosis of MPIAP on the basis of FC concentrations is subject to considerable error, due to the high individual variability of this indicator. FZRP is a better parameter, but this needs further research, as these are the first determinations in infants with MPIAP.