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Are Transcutaneous Bilirubin Measurements Reliable During or After Phototherapy?

November 27, 2023

We see a lot of newborns in our practice—and so we do a lot of transcutaneous bilirubin (TCB) measurements. It’s much less traumatic for the infant and parents when we can just touch the skin with the bilirubinometer than it is for us to get blood from the infant for a total serum bilirubin (TSB).

One of the times when we cannot use TCB measurements is when the infant is receiving or has recently received phototherapy for hyperbilirubinemia, because there is concern that the TCB measurements are unreliable.

But is that actually true?

This week, an article being early released in Pediatrics by Dr. Lisa ten Kate and colleagues from 4 institutions in Suriname and the Netherlands entitled, “Transcutaneous Bilirubin Accuracy Before, During, and After Phototherapy: A Meta-Analysis,” tackles this question (10.1542/peds.2023-062335). 

The authors reviewed the literature and conducted a meta-analysis of studies that compared TCB and TSB before, during, and after phototherapy.

For those who are not as familiar with phototherapy, it involves shining bright lights on the infant. The phototherapy works by converting unconjugated bilirubin into a form that is water-soluble and can be removed from the body in the urine and stool. For phototherapy to be maximally effective, as much of the infant’s skin as possible should be exposed to the light. So generally, only the infant’s eyes and perhaps the genital area are covered.

The authors found that use of the TCB was reasonably reliable before and during phototherapy, but there were not enough data to determine the reliability of the TCB after phototherapy. The authors also noted that for TCB to be most reliable during phototherapy, it should be measured on covered skin—which I assume means skin that is not exposed to phototherapy. They mention the forehead as most reliable, and the forehead between the eyes would have been covered during phototherapy.

It is helpful to know that forehead TCB measurements before and during phototherapy are reliable. However, until we have more data, we still need to rely on TSB measurements after phototherapy.

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