title: The age of necrotizing enterocolitis onset: an application of Sartwell's incubation period model.
abstract: OBJECTIVE
  Model age of necrotizing enterocolitis (NEC) onset applying Sartwell's model of incubation periods, and examine its relationship to gestational age (GA).
  
  
  METHODS
  Retrospective chart review of St Louis Children's Hospital neonates diagnosed with NEC (≥Bell's stage II) from 2004 to 2008, inclusive.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Gastroenterology, St Louis Children's Hospital, Department of Pediatrics, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: R
authors.initials: R
authors.lastname: González-Rivera
authors.forename: R C
authors.initials: RC
authors.lastname: Culverhouse
authors.forename: A
authors.initials: A
authors.lastname: Hamvas
authors.forename: P I
authors.initials: PI
authors.lastname: Tarr
authors.forename: B B
authors.initials: BB
authors.lastname: Warner
mesh_terms: D017668:Age of Onset; D020345:Enterocolitis, Necrotizing / Q000453:epidemiology*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D055256:Infectious Disease Incubation Period; D008297:Male; D015233:Models, Statistical; D017711:Nonlinear Dynamics