Authors 

Claire Howarth; Joan Morris; Christian Mifsud; Jayanta Banerjee; Terence Leung; Simon Eaton; Narendra Aladangady  

Institution(s) 

1.Homerton University Hospital NHS Foundation Trust, London; 2. Queen Mary University of London, London; 3.St George’s, University of London, London; 4. UCL,Great Ormond Street Institute of Child Health, London; 5. Imperial College Healthcare NHS Trust, London; 6.Imperial College London; 7. University College London, London. 

Introduction (include hypothesis) 

Survival of very preterm infants has improved¹, but the incidence of NEC has not changed². Progress in the prevention of NEC has been limited by difficulties in clearly defining high risk groups, variable definitions of NEC and a lack of routinely used effective gut biomarkers.  Near Infrared Spectroscopy (NIRS) can non-invasively measure regional oxygenation.  We aimed to establish if gut biomarkers of tissue injury and measurements of regional oxygenation differ in infants with NEC compared to those without, and whether they could predict the onset of NEC. 

Methods

We examined 48 infants <30w gestational age (GA) admitted to our tertiary level NICU from Oct 2016 to May 2018.  Exclusion criteria: birthweight ≤2^nd centile, abnormal antenatal dopplers, major congenital anomalies or Twin to Twin Transfusion Syndrome.  For 60 minutes each week, splanchnic (sTOI) and cerebral (cTOI) Tissue Oxygenation Index (TOI) were measured simultaneously using NIRO-300 (Hamamatsu KK, Japan). Subsequently splanchnic (sFTOE) and cerebral (cFTOE) Fractional 

Tissue Oxygenation (FTOE) were calculated. Weekly urinary intestinal and liver fatty acid binding proteins (I- FABP, L-FABP), Trefoil Factor 3 (TFF3) and stool Calprotectin were measured by ELISA and weekly clinical status recorded for the first 8 weeks of life. NEC was defined as ≥ Bells stage 2. Statistical analysis was completed using STATA/SE version 15.1. 

Results 

Median birthweight was 884g (460-1600), median GA 26⁺³ weeks (23⁺⁰-29⁺⁶) and 52% were female. 7 infants developed NEC. There was a wide variation in normal ranges of all 4 gut biomarkers and none were affected by confounders.  L-FABP had significantly lower values in 28-29w compared to 23w (p=0.01), others were not affected by GA, but for all biomarkers chronological age was important. Cerebral TOI was significantly higher than sTOI over the first 8 weeks of life (p<0.0001). There were no statistically significant differences in any biomarker level between those with, and without NEC (all p>0.05), but there were significant differences in NIRS measurements (Table 1) and these persisted when adjusted for confounders (GA, gender, PDA, enteral feeds, ethnicity and Hb). 

NIRS  measurements	Non – NEC infants Mean (95% CI)	NEC infants Mean (95% CI)	Mean difference (95% CI)	P value
sTOI (%)	43.6 (41.2-46.0)	33.6 (27.3 – 39.9)	-9.3 (-18.0 to -0.50)	0.038
sFTOE	0.53 (0.50-0.56)	0.64 (0.56-0.71)	0.11 (0.01 to 0.20)	0.031
cTOI (%)	63.9 (62.2-65.5)	56.9 (53.2-60.6)	-6.6 (-11.7 to -1.5)	0.011
cFTOE	0.30 (0.28-0.32)	0.38 (0.33-0.43	0.08 (0.02 to 0.14)	0.009

Conclusions

Gut biomarker levels in preterm infants demonstrate a wide variation in normal ranges and we did not identify any gut tissue biomarkers that could predict NEC.  Infants who developed NEC had significantly lower sTOI and cTOI throughout their neonatal intensive care stay. Further research is needed to examine whether NIRS monitoring coupled with intervention can improve outcomes.  Perhaps the future of NEC prediction is an algorithm using machine learning combining clinical, laboratory, and radiological features, as well as NIRS and biomarker information. 

References  

1) Costoloe, K., et al., Short term outcomes after extreme preterm birth in England: comparison of two birth cohorts in 1995 and 2996 (EPICure studies). BMJ, 2012. 345: p. e7976. 2) Costoloe, K., et al., Probiotics in Preterm Infants Study Collaborative G. Bifidobacterium, breve BBG-001 in very preterm infants: a randomised controlled phase 3 trial. Lancet, 2016. 387: p. 649-660.