The age of necrotizing enterocolitis onset: an application of Sartwell's incubation period model

Objective: Model age of necrotizing enterocolitis (NEC) onset applying Sartwell's model of incubation periods, and examine its relationship to gestational age (GA). Study Design: Retrospective chart review of St Louis Children's Hospital neonates diagnosed with NEC (>= Bell's stage II) from 2004 to 2008, inclusive. Result: The relationship between age of NEC (N - 84 cases) onset and GA best fits a non-linear model, with infants <= 28 weeks having a disproportionately longer time to onset than older GA groups and explained 50.3% of the variability in age of NEC onset. Additional clinical variables provided no improvement in explaining age of NEC onset. Application of Sartwell's model to age of NEC onset proved a good fit, when birth is used as the common exposure episode, and age is equivalent of the incubation period. Conclusion: The relationship between day of NEC diagnosis and GA is non-linear, with lower GA infants having disproportionately longer time to onset. Despite these GA differences, the fit to Sartwell's model for incubation periods model is consistent with NEC being a consequence of an event that occurs at or soon after birth. Journal of Perinatology (2011) 31, 519-523; doi:10.1038/jp.2010.193; published online 27 January 2011