title: Interpreting conjugated bilirubin levels in newborns.
abstract: OBJECTIVE
  To examine the clinical significance of elevated conjugated bilirubin (CB) levels in newborns.
  
  
  METHODS
  This retrospective study evaluated a birth cohort of 271 186 full-term newborns born within a Northern California hospital network from 1995 to 2004. All CB and direct bilirubin (DB) levels were available in a database and were correlated with the patients' inpatient and outpatient International Classification of Diseases, 9th Revision diagnoses.
  
  
  RESULTS
  The 99th percentile for CB is 0.5 mg/dL, and the 99th percentile for DB is 2.1 mg/dL. CB levels between 0.5 and 1.9 mg/dL can be associated with infection, but most often remain unexplained. Liver and biliary disease become increasingly likely as CB levels increase; for CB ≥5 mg/dL, 47% of newborns have biliary disease and 43% have liver disease.
  
  
  CONCLUSIONS
  CB and DB levels are not interchangeable. In newborns with CB levels ≥0.5 mg/dL and <2 mg/dL, infection must be ruled out, and the newborn should be observed. In newborns with levels ≥2 mg/dL, a more in-depth assessment of the hepatobiliary system is indicated.
authors.affiliation: Department of Pediatrics, California Pacific Medical Center, San Francisco, CA, USA. arahnd@gmail.com
authors.forename: Adam Rahn
authors.initials: AR
authors.lastname: Davis
authors.forename: Philip
authors.initials: P
authors.lastname: Rosenthal
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Escobar
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Newman
mesh_terms: D001663:Bilirubin / Q000097:blood*; D002779:Cholestasis / Q000175:diagnosis; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007567:Jaundice, Neonatal / Q000175:diagnosis; D008297:Male; D012016:Reference Values; D012189:Retrospective Studies
chemical_list: D001663:Bilirubin