Purpose of study Calprotectin is a granulocyte protein that can be found in stool. Studies by our group and others show higher calprotectin values in stools of neonates with necrotizing enterocolitis (NEC) than in stools of healthy term infants. However, that comparison is flawed because NEC typically occurs in growing premature, not healthy term, neonates. Therefore we created calprotectin reference intervals based on gestational and postnatal age, and evaluated whether a level above the upper reference interval on the new charts is diagnostic for NEC. Methods used To create proper reference intervals, we measured calprotectin in stools of premature neonates of various gestational and post-natal ages who had no known gastrointestinal pathology. Levels from infants undergoing a ‘rule out NEC’ evaluation were then plotted on the new charts, and whether or not the infant had NEC was judged by the responsible clinician days/weeks later. Summary of results Charts based on 249 stool measurements display calprotectin reference intervals on the day of birth according to gestational age and during the first 8 weeks after birth. The 90th percentile exceeded 200 mg/g stool for all gestational and postnatal ages. Levels at birth were lower in those 24–29 weeks gestation at birth than 30–34 weeks gestation at birth (p=0.007), and were lower in the first week than in the second through eighth weeks (p<0.001). Calprotectin levels during ‘rule out NEC’ evaluations (n=118) were above the reference interval in 59% of those where NEC was documented and in 17% where NEC was judged to be unlikely (p<0.001). Conclusions Stool calprotectin from preterm neonates with no signs of intestinal pathology have a wider range and higher upper reference interval than do stools of healthy children and adults. Among neonates undergoing a ‘rule out NEC’ evaluation, a stool calprotectin level above the upper interval for age supports the likelihood that the problem is NEC, but this test is not sufficiently specific to independently confirm a diagnosis of NEC.
B. MacQueen, R. Christensen, C. Yost
Journal of Investigative Medicine