title: Using axillary temperature to approximate rectal temperature in newborns.
abstract: OBJECTIVE
  Various factors have been shown to potentially affect the difference between axillary and rectal temperature measurements in newborns. We aimed to explore their roles and, if possible, to construct a formula that explained the difference.
  
  
  METHODS
  The study was based on a consecutive sample of 175 infants, with a gestational age of 24-42 weeks, whose rectal and axillary temperatures were measured simultaneously at the neonatal unit at Skaraborg Hospital in Sweden. Data were analysed using multiple regressions.
  
  
  RESULTS
  Premature infants had a significantly smaller mean difference (0.33°C) between rectal and axillary temperatures than full-term infants (0.43°C). Significant associated factors for premature infants were chronological age (p = 0.025), time of day (p = 0.004) and axillary temperature (p < 0.001). For full-term infants, the only significant associated factor was axillary temperature (p = 0.015).
  
  
  CONCLUSIONS
  Although it is possible to construct a formula that estimates neonate rectal temperature based on axillary temperature with a slightly higher reliability than simply adding a fixed value like 0.4°C, such a formula would be too complex to apply in practice. Adding 0.3°C or 0.4°C to the measured axillary temperature for premature infants or full-term infants, respectively, yields acceptable approximations in most cases.
authors.affiliation: Department of Technology Management and Economics, Chalmers University of Technology, Gothenburg, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Lantz
authors.affiliation: Neonatology Division, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Ottosson
mesh_terms: D001365:Axilla; D001831:Body Temperature; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D010808:Physical Examination / Q000379:methods; D012007:Rectum
keywords: Axillary temperature; Neonate; Rectal temperature; Thermometry methods