Immunoreactive trypsin levels in neonates with meconium ileus

Serum immunoreactive trypsin (IRT) is used as a screening test for cystic fibrosis (CF) in neonates in many countries. Variations in IRT levels are observed in healthy and cystic neonates within the first few weeks of life. Fifteen percentage of CF neonates present with meconium ileus (MI). We hypothesised that there may be differences in serum IRT levels in cystic babies with simple and complicated MI. The aim of this study was to investigate the serum levels of IRT in neonates with CF presenting with MI. IRT levels were sequentially measured in neonates (n = 29) with CF with intestinal obstruction due to simple or complicated MI. These were compared to levels obtained from non-cystic neonates/controls admitted with a variety of other intra-abdominal pathologies (n = 49) IRT levels were significantly higher in the CF-MI group than the non-cystic controls (P < 0.001). There was no statistical difference in IRT levels between the simple or complicated MI groups. In the MI group there was no statistical difference between those who required operation, no difference between the pre- and post-operative IRT levels and no significant relationship between IRT levels and birth weight or gestation. Serum IRT levels are significantly elevated in neonates with CF and MI compared with non-cystic, non-MI neonates. The results of this observational study highlight that a single raised level of IRT in a neonate should prompt the analysis for CF regardless of any underlying surgical pathology.