Fecal Calprotectin in Healthy Term and Preterm Infants

To the Editor: Fecal calprotectin is a useful marker of bowel inflammation in adults and children. Recent studies show an age-dependent variation in fecal calprotectin in children. Increased fecal calprotectin levels have been reported in young infants (1–4). The small amount of feces (50–100 mg) necessary for the measurement of fecal calprotectin by enzyme-linked immunosorbent assay (ELISA) makes this test potentially useful in preterm infants. Because necrotizing enterocolitis (NEC) primarily affects preterm infants, fecal calprotectin measurements could be a valuable tool for the investigation of preterm infants suspected of having NEC. Because no data on this test are available for preterm infants, we measured fecal calprotectin in healthy term and preterm infants. Between April and July 2002, spot stool samples of 11 healthy preterm (mean age, 31 weeks; range, 25–25 weeks) and 16 healthy full-term infants (mean age, 39 weeks; range, 37–42 weeks) were collected. Results were compared with those of 18 children with treated inflammatory bowel disease (IBD) (mean age, 14 years; range, 7–17 years) and 21 control children (mean age, 7 years; range, 1–15 years) available in our laboratory. The stool samples of the preterm and full-term infants were collected between days 3 and 18 after birth. Exclusion criteria were infections, congenital anomalies, and respiratory insufficiency. Except for the preterm infants, spot samples of feces (1–2 g) were collected at home, placed in a plastic stool container and sent by mail to the laboratory. Stool samples were frozen on receipt at −20°C within 48 hours of collection. Before analysis, the frozen stool samples were thawed at room temperature. Fecal calprotectin was measured by an ELISA kit (Calprest™) according to the manufacturer's instructions. Calprotectin (median [interquartile range]) levels in healthy full-term infants, preterm infants, patients with IBD, and control subjects were 235 μg/g feces (range, 172–2880 μg/g), 150 μg/g (range, 81–221 μg/g), 237 μg/g (range, 40–8575 μg/g) and 17 μg/g range (7–41), respectively. Results are shown in Figure 1. When the four groups were analyzed simultaneously by variance analysis, a significant between-group difference was found (P < 0.0001). No difference was found between the IBD and either newborn group. A significant difference was found between our control group and our IBD (P < 0.001), full-term (P < 0.001 ), and preterm (P < 0.001) groups.FIG. 1.: Boxplot of fecal calprotectin concentration: preterm (n = 11) and full term (n = 16) infants, control children (n = 21) and children with inflammatory bowel disease (n = 18). Note the logarithmic scale of the vertical axis. The boxplot shows the median (central horizontal line), the 10th centile (lower box border), the 90th centile (upper box border). The upper and lower horizontal lines refer to the 95th and 5th centile respectively. Outliers (above the 95th or below the 5th centile) are designated with a black dot.The fecal calprotectin levels in preterm and full-term infants < 3 weeks old were similar to those of children with treated IBD. Whether fecal calprotectin in preterm infants might be used to diagnose NEC is questionable as no data are available on fecal calprotectin levels in preterm infants with NEC. The high levels and the wide interindividual variation in fecal calprotectin in preterm and term infants probably preclude its use for early detection of NEC, unless patients with NEC have extremely high fecal calprotectin. *Annemieke C. Nissen *Carlijn E. van Gils †Paul P. Menheere *Anita. M. Van den Neucker *Mark A. van der Hoeven *Pierre-Philippe Forget