Age-Dependent Variations in Fecal Calprotectin Concentrations in Children

Abstract

To the Editors: As have Olafsdottir et al. (1) and Rugtveit and Fagerhol (2), we have studied the change in fecal calprotectin concentration over the first year of life (3). However, our 80 infants were studied longitudinally at monthly intervals from 1 week old, and we used the same “in-house” method of measuring and expressing the values as we used for studies described in our two recent papers (4,5), not the commercial kit method. Therefore, the actual numbers cannot be compared directly with those described by Rugtveit and Fagerhol (2). Yet, we found the same trend, with infants younger than 3 months showing higher values than those between 6 and 12 months of age, and those between 6 and 12 months of age showing higher concentrations than our child controls, aged 1.5 to 15.3 years. We found that fecal calprotectin concentration significantly increased from 1 week to 1 month of age and then progressively fell until 12 months. Additionally, fecal calprotectin concentration was significantly lower in breast-fed than in formula-fed infants at each age, even after weaning began. Breast-feeding has been reported to be immunosuppressive (6) and, compared with formula feeding, is associated with a more rapid decrease in permeability. Either or both of these may be responsible for the lower fecal calprotectin concentration in breast-fed infants. In fact, fecal calprotectin concentration in this young age group may provide useful insight into the developing mucosal immune system. Knowing how the reference range for fecal calprotectin concentration varies with age is valuable information. This is why we established and used our child control range as part of our first inflammatory bowel disease study (4) and quoted it for the second study (5). Children with inflammatory bowel disease rarely are diagnosed younger than 2 years old, and our youngest recruit with inflammatory bowel disease was 4.3 years old. Therefore, we used the appropriate reference range. Further investigation of the use of fecal calprotectin concentration to assess gut inflammation in infancy must consider the wider and higher ranges demonstrated, but also the differences in breast-fed and formula-fed infants. Barbara Golden Su Bunn Margaret Main