Age-Dependent Variations in Fecal Calprotectin Concentrations in Children

To the Editors: The fecal concentration of calprotectin, a dominating protein in the cytosol of neutrophil granulocytes, has been associated with the degree of disease activity in inflammatory bowel disease in adults (1,2) and in children (3). This protein is stable in the feces for 1 week at room temperature (4), and commercial ELISA kits are available for extraction and analysis of small (approximately 0.1 g) stool samples (5). The test has great potential as a tool for the pediatric gastroenterologist, for example, in differentiating between inflammatory and functional diseases of the intestine. In a recent study of 27 healthy infants, 2 to 10 weeks of age (6), surprisingly high values were found. This points to the obvious need for reference values for the different age groups. Therefore, we report the result from analyzing fecal calprotectin in 115 presumably healthy children visiting two local community health centers in Oslo for routine examinations. The analysis was performed, as previously described (4), using a simple extraction procedure (7) having an upper reference of 50 mg/kg in healthy adults. The children were divided into six age groups, from 6 weeks to 5 years, (Table 1). The values found in the first year of life were similar to those that Olafsdottir et al. (6) found and similar to values found in older children (8) and adults (9) with inflammatory bowel disease. The variation within each age group, especially in the youngest, is impressive (Fig. 1). This variation does not seem to be caused by a variation among samples from the same individual from one day to another (6). No accumulation of calprotectin-rich leukocytes occurs in the healthy intestinal mucosa in the first months of life or later; therefore, the high calprotectin concentrations found, especially in some of the children in the youngest age groups, may reflect increased migration of neutrophil granulocytes into the gut lumen in early life. Development of the gut immune system and establishment of a normal bacterial flora in the first weeks and months of life may be among the factors behind this interesting variation.TABLE 1: Faecal calprotectin in healthy childrenFIG. 1.: The calprotectin concentration found in fecal samples from 115 presumably healthy children at routine health control at two community health centers in Oslo.We also present the results in Table 1 for convenient use as reference values. The data presented here will be useful when evaluating fecal calprotectin concentrations in children with abdominal symptoms. Among children in the age groups 2 years and 5 years, 6 of 19 and 0 of 15, respectively, had fecal calprotectin concentrations between 200 and 400 mg/kg, which may be found in patients with inflammatory bowel disease in stages with little or no disease activity. In clinical relapses, concentrations typically are above 1,000 mg/kg. *Jarle Rugtveit †Magne K. Fagerhol