The second Canadian study enrolled 774 infants born at ≥ 37 weeks gestational age in Calgary and assessed TcB with the JM-103.4 Infants were categorized as having light (n = 347), medium (n = 412), and dark (n = 15) skin tones by study nurses, based on reference cosmetic colors. All infants had paired TcB and TSB measurements within 60 minutes of each other and before 120 hours of life.
Multivariate linear regression analysis using medium skin tone as the reference group found a tendency toward low TcB levels in infants with light skin tone and a tendency toward high TcB levels in infants with dark skin tone (adjusted R2 = 0.86). The AUC was ≥ 0.95 for all ROC curves for lightand medium-toned infants at key TSB cutoff points; the study included too few infants with dark skin tone to generate ROC curves for that group.4
Recommendations from others
In 2009, the American Academy of Pediatrics (AAP) recommended universal predischarge screening for hyperbilirubinemia in newborns using either TcB testing or TSB. The AAP statement did not address the effect of skin tone on TcB levels, but did advise regular calibration of TcB and TSB results at the hospital level.5
In 2016, the National Institute for Health and Care Excellence (NICE) updated their guideline on jaundice in newborns younger than 28 days old. NICE recommended visual inspection of all babies for jaundice by examining them in bright natural light and looking for jaundice on blanched skin; it specifically advised checking sclera and gums in infants with darker skin tones.6
The Nigerian researchers noted earlier have published an updated TcB nomogram for their patient population.7
Editor’s takeaway
Even with the small variation of 2 mg/dL or less between transcutaneous and serum bilirubin, and the SOR of C due to lab values being labeled disease-oriented evidence, TcB proves to be useful. In practice, concerning TcB values should lead to serum bilirubin confirmation. This evidence indicates we might be ordering TSB measurements more or less often depending on skin tone, reinforcing the need for review and adjustment of TcB cut-off levels based on the local population.