title: Limitations and opportunities of transcutaneous bilirubin measurements.
abstract: OBJECTIVE
  Although transcutaneous bilirubinometers have existed for over 30 years, the clinical utility of the technique is limited to a screening method for hyperbilirubinemia, rather than a replacement for invasive blood sampling. In this study, we investigate the reason for this limited clinical value and address possibilities for improvement.
  
  
  METHODS
  To obtain better insight into the physiology of bilirubin measurements, we evaluated a transcutaneous bilirubinometer that determines not only the cutaneous bilirubin concentration (TcB) but also the blood volume fraction (BVF) in the investigated skin volume. For 49 neonates (gestational age 30 ± 3.1 weeks, postnatal age 6 [4-10] days) at our NICU, we performed 124 TcB and 55 BVF measurements.
  
  
  RESULTS
  The TcB correlated well with the total serum bilirubin concentration (TSB) (r = 0.88) with an uncertainty of 55 µmol/L. The BVF in the measured skin volume ranged between 0.1% and 0.75%.
  
  
  CONCLUSIONS
  The performance of our bilirubinometer is comparable to existing transcutaneous devices. The limited clinical value of current bilirubinometers can be explained by the low BVF in the skin volume that is probed by these devices. Because the TcB depends for over 99% on the contribution of extravascular bilirubin, it is a physiologically different parameter from the TSB. Hence, the standard method of evaluation that compares the TcB to the TSB is insufficient to fully investigate the clinical value of transcutaneous bilirubinometers, ie, their predictive value for kernicterus. We suggest that the clinical value may be improved considerably by changing either the method of evaluation or the technological design of transcutaneous bilirubinometers.
authors.affiliation: Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands. n.bosschaart@amc.uva.nl
authors.forename: Nienke
authors.initials: N
authors.lastname: Bosschaart
authors.forename: Joke H
authors.initials: JH
authors.lastname: Kok
authors.forename: Astrid M
authors.initials: AM
authors.lastname: Newsum
authors.forename: Dagmar M
authors.initials: DM
authors.lastname: Ouweneel
authors.forename: Rosaline
authors.initials: R
authors.lastname: Mentink
authors.forename: Ton G
authors.initials: TG
authors.lastname: van Leeuwen
authors.forename: Maurice C G
authors.initials: MC
authors.lastname: Aalders
mesh_terms: D001663:Bilirubin / Q000097:blood*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D007567:Jaundice, Neonatal / Q000097:blood / Q000175:diagnosis*; D008297:Male; D015997:Neonatal Screening / Q000379:methods*; D011237:Predictive Value of Tests; D012372:ROC Curve; D013057:Spectrum Analysis / Q000379:methods* / Q000639:trends
chemical_list: D001663:Bilirubin