Jaundice an unreliable method of predicting the baby's risk of hyperbilirubinemia

Mar 23 2009

For hundreds of years, doctors, nurses and midwives have visually examined newborn babies for the yellowish skin tones that signify jaundice, judging that more extensive jaundice carried a greater risk of illness.

The yellowness comes from a blood byproduct, bilirubin, and a child that develops high levels of bilirubin has a potentially serious condition called hyperbilirubinemia.

Now pediatric researchers say that this longstanding practice of visual inspection is an unreliable method of predicting the baby's risk of hyperbilirubinemia. Only infants with a total absence of visible jaundice can confidently be expected to have a very low risk of hyperbilirubinemia.

"Our study tells clinicians that our ability to estimate a baby's bilirubin level, or predict the baby's risk of developing clinically significant hyperbilirubinemia, by visually observing the extent of visual jaundice, is inadequate, and not very helpful," said study leader Ron Keren, M.D., M.P.H., a pediatrician in the Center for Pediatric Clinical Effectiveness at The Children's Hospital of Philadelphia. Keren also is a faculty member of the University of Pennsylvania School of Medicine.

The study appeared March 22 in the online version of Archives of Disease in Childhood -- Fetal and Neonatal Edition .

Neonatal jaundice is very common, occurring in as many as 60 percent of newborns annually, according to the American Academy of Pediatrics. It appears as a yellow skin color, a sign of excess bilirubin, a byproduct of the normal breakdown of red blood cells. In the vast majority of cases, jaundice disappears in one to two weeks as the baby's liver reduces bilirubin to normal levels, permitting the excess to be excreted.

But extremely high levels of bilirubin can cause kernicterus, a potentially life-threatening condition that can result in long-term brain damage, hearing loss and other neurological problems. Although extremely rare, kernicterus has been increasing in the U.S. over the past two decades, leading some professional organizations to advocate universal bilirubin screening before newborns leave the hospital. The standard treatment for significant hyperbilirubinemia is phototherapy-exposing the baby to ultraviolet lights that chemically change bilirubin under the skin to a harmless form.

The current study was the first systematic analysis of jaundice assessment as a predictor of significant hyperbilirubinemia risk. It was also the largest such study, involving 522 term and late-preterm newborns.

Clinicians have long known that neonatal jaundice progresses from head to foot, as shown by yellowing of the baby's skin. In this study, conducted in the Well Baby Nursery of the Hospital of the University of Pennsylvania, nurses used a five-point scale to grade the farthest extent of jaundice along the newborn's body. The nurses who did the ratings did not know the actual bilirubin levels, which were measured by other caregivers using a noninvasive device.

On analyzing the results, the researchers found that, while there was some correlation between the extent of jaundice as rated by the nurses and the measured bilirubin levels, the extent of jaundice could not be used to estimate the bilirubin level or to accurately predict an infant's risk of developing significant hyperbilirubinemia (defined in this study as a bilirubin level for which phototherapy is recommended). Furthermore, contrary to a common belief that it is harder to visually assess jaundice in dark-skinned infants, there was no significant difference in the results between black and white newborns.

The correlation between visually assessed jaundice and bilirubin level was especially weak in late-preterm infants, those at 35 to 38 weeks gestational age. This is important, said Keren, because late-preterm infants are at greater risk of developing significant hyperbilirubinemia.

The one exception to the poor predictive value of visual assessment came in the 91 infants (17 percent of all those studied) rated by the nurses as having a complete absence of jaundice. For those infants, the actual risk of developing significant hyperbilirubinemia was extremely low, less than 1 percent. Even for those infants, said Keren, absence of visual jaundice may require a caveat. "Less experienced observers may be less capable of accurately assessing a complete absence of jaundice. All in all, the benefits of objective results from universal bilirubin screening may outweigh the benefit in reducing testing and costs from pursuing a selective screening approach."

Funding for the study came from the National Institute of Child Health and Human Development of the National Institutes of Health. Respironics of Murrysville, Pa, provided medical devices and equipment for the study. Keren's co-authors were Katie Tremont, B.S., and Xianqun Luan, M.S., both of Children's Hospital; and Avital Cnaan, Ph.D., of both Children's Hospital and the University of Pennsylvania.

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