Abstract
Introduction: Inflammatory bowel disease (IBD), encompassing Crohn Disease (CD) and ulcerative colitis (UC), is an incurable condition characterized by chronic relapsing and remitting gut symptoms. Better ways to detect and monitor active disease are required, to enable early diagnosis and to optimize care and outcomes, particularly for children. Current methods include endoscopic evaluations and the routinely used biomarker faecal calprotectin (fCal). fCal can be limited by variability in younger children. Recent work has demonstrated that faecal MPO (fMPO), a neutrophil granule enzyme is an accurate marker of disease activity in children with CD and may be superior to fCal. This study assessed the variability of fCal and fMPO levels in healthy preschool age children.
Methods: Calprotectin was measured by commercial ELISA and MPO was measured by in-house sandwich ELISA in faecal samples from children aged between 2-6 years reported as healthy by their parent or caregiver. fMPO activity was ascertained enzymatically. Spearman r correlation was used to determine any relationship between fCal and fMPO, or between each faecal marker and age. Differences in faecal markers between sex were assessed by unpaired t-test.
Results: There was large variability in fCal concentrations in this cohort of 63 children, with a median fCal concentration of 28.76 ug/g (range of 3.84 - 897.1 ug/g). The mean fCal concentration was 74.1 ug/g, above the clinically accepted cut-off of 50 ug/g indicative of active inflammation. fCal was elevated (> 50 ug/g) in samples from 22 children (35% of the cohort). Alternatively, the median concentrations of fMPO activity and fMPO protein were both 0.00 ug/g, while the means were 0.42 and 1.10 ug/g, respectively, indicating less variability in fMPO levels. There was no correlation between fCal or fMPO concentration and age, and no difference in faecal marker concentrations between males and females (p>0.05). fCal correlated with fMPO activity (r=0.45, =0.0002) and fMPO protein (r=0.41, p=0.001).
Conclusions: There was large variation in levels of fCal in this healthy preschool age cohort while fMPO levels were less variable. These results highlight the potential limitations of using fCal to determine potential gastrointestinal inflammation in young children. As a result, fMPO may be a superior non-invasive marker to use in the paediatric setting, with further research into this area warranted.