title: Reference chart for relative weight change to detect hypernatraemic dehydration.
abstract: OBJECTIVE
  The validity of the rule of thumb that infants may have a weight loss of 10% in the first days after birth is unknown. We assessed the validity of this and other rules to detect breast-fed infants with hypernatraemic dehydration.
  
  
  METHODS
  A reference chart for relative weight change was constructed by the LMS method. The reference group was obtained by a retrospective cohort study.
  
  
  METHODS
  1544 healthy, exclusively breast-fed infants with 3075 weight measurements born in the Netherlands and 83 cases of breast-fed infants with hypernatraemic dehydration obtained from literature.
  
  
  RESULTS
  The rule of thumb had a sensitivity of 90.4%, a specificity of 98.3% and a positive predictive value of 3.7%. Referring infants if their weight change is below -2.5 SDS (0.6th centile) in the reference chart in the first week of life and using the rule of thumb in the second week had a sensitivity of 85.5%, a specificity of 99.4% and a positive predictive value of 9.2%.
  
  
  CONCLUSIONS
  The rule of thumb is likely to produce too many false positive results, assuming that for screening purposes the specificity needs to be high. A chart for relative weight change can be helpful to detect infants with hypernatraemic dehydration.
authors.affiliation: TNO Quality of Life, Leiden, The Netherlands. P.vanDommelen@pg.tno.nl
authors.forename: Paula
authors.initials: P
authors.lastname: van Dommelen
authors.forename: Jacobus P
authors.initials: JP
authors.lastname: van Wouwe
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Breuning-Boers
authors.forename: Stef
authors.initials: S
authors.lastname: van Buuren
authors.forename: Paul H
authors.initials: PH
authors.lastname: Verkerk
mesh_terms: D001942:Breast Feeding; D003681:Dehydration / Q000175:diagnosis* / Q000453:epidemiology; D004812:Epidemiologic Methods; D019317:Evidence-Based Medicine; D005260:Female; D006801:Humans; D006955:Hypernatremia / Q000175:diagnosis* / Q000453:epidemiology; D007224:Infant Care / Q000379:methods*; D007231:Infant, Newborn; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D012016:Reference Values; D012017:Referral and Consultation; D015431:Weight Loss