Intestinal Biomarkers in Preterm Infants: Influence of Mother’s Own Milk on Fecal Calprotectin and of Gestational Age on IFABP Concentrations

<b>Background/Objectives:</b> Calprotectin and intestinal fatty acid-binding protein (IFABP) may reflect the intestinal maturation process of very preterm infants (VPI) but have also been associated with gut inflammation. To establish normative values for fecal calprotectin (FC) and urinary intestinal fatty acid-binding protein (uIFABP) in VPI and to study their correlations with demographic and clinical factors. <b>Methods:</b> A cohort of VPI (born before or at 32.0 weeks of gestation) was recruited in two neonatal intensive care units. Urine and fecal samples were collected at 1, 4 and 8 weeks of life to measure urinary IFABP (normalized to creatinine as uIFABP/Cr) and FC, respectively. UIFABP was determined by ELISA and FC by fluoroenzyme immunoassay. <b>Results</b>: 194 newborns had at least one valid biomarker measurement. The study cohort mean gestational age was 28.9 ± 2.3 weeks and mean birth weight 1178 ± 365 g. Although uIFABP/Cr concentrations differed between the two centres, they were negatively correlated with gestational age, with a statistically significant correlation observed in both centres at week 4 (Hospital Clínic: Spearman's rho -0.500; <i>p</i> = 0.000 and Hospital Sant Joan de Déu: Spearman's rho -0.474; <i>p</i> = 0.000). Conversely, FC showed a positive significant correlation at the same time point (Spearman's rho 0.302; <i>p</i> = 0.006). At week one, FC increased with antibiotic exposure (28 mcg/g of stool per antibiotic day, 95%CI 3-57; <i>p</i> = 0.028). FC at week 4 was inversely correlated with mother's own milk (MOM) exposure during the first month (Spearman's rho -0.253; <i>p</i> = 0.023). <b>Conclusions</b>: uIFABP/Cr and FC are associated with gestational age at 4 weeks and FC is also influenced by antibiotic treatment and MOM exposure.