Which lab test best predicts auditory impairment in infant hyperbilirubinemia?

Last Updated: 2017-09-27

By Marilynn Larkin

NEW YORK (Reuters Health) - Unbound bilirubin, but not total serum bilirubin (TSB) or bilirubin albumin molar ratio, is associated with chronic auditory toxicity in late preterm and term infants, researchers say.

Significant unconjugated hyperbilirubinemia, among the most common readmission diagnoses for neonates worldwide, is considered a sentinel event, according to Dr. Sanjiv Amin of Rochester University in New York and colleagues.

"An urgent therapeutic intervention is needed to prevent acute bilirubin encephalopathy that can result in death or kernicterus, including permanent sensorineural hearing loss," they state. Yet current guidelines for handling significant unconjugated hyperbilirubinemia are based on limited evidence, and current biochemical measures may not accurately predict chronic auditory toxicity or kernicterus.

"In earlier studies in India and in the U.S., (we) had shown that unbound bilirubin was a more specific and sensitive predictor than TSB of acute auditory toxicity when evaluated during the neonatal period," Dr. Amin told Reuters Health by email.

For the current prospective study, also conducted in India, the team compared how well unbound bilirubin, TSB, and bilirubin albumin molar ratio predict chronic auditory toxicity.

The investigation, reported online September 27 in Pediatrics, involved 93 neonates (mean gestational age, 37.4 weeks; 55 boys) with significant hyperbilirubinemia in the first two postnatal weeks. Significant hyperbilirubinemia was defined as TSB of at least 20 mg/dL or TSB that met criteria for exchange transfusion.

The infants underwent auditory evaluations at 2-3 months and 9-12 months of age. None had an interval history of head trauma, malignancy or meningitis, and none had middle-ear disease.

Twelve of the infants had chronic auditory toxicity - three with auditory neuropathy spectrum disorder (ANSD), four with sensorineural hearing loss (SNHL), and five with both conditions. Ten of the 12 had been previously diagnosed with acute auditory toxicity; two had a normal auditory evaluation soon after the significant hyperbilirubinemia resolved. Of the nine infants with SNHL, four had severe-to-profound hearing loss of >70 dB.

Among the 81 infants without chronic auditory toxicity, 16 had been diagnosed with acute auditory toxicity during the neonatal period.

The positive and negative predictive values of neonatal auditory evaluations for subsequent chronic auditory toxicity were 0.38 and 0.97, respectively.

After adjustment for covariates, peak unbound bilirubin - but not peak TSB or peak bilirubin albumin molar ratio - was significantly associated with auditory toxicity (odds ratio, 2.41).

"Although the longitudinal study was performed in India because of the high prevalence of significant jaundice (there)," Dr. Amin explained in an email to Reuters Health, "this has global health implications, irrespective of gender, race and ethnicity."

Dr. Amanda Lovering, an audiologist at Children's Health and UT Southwestern in Dallas, told Reuters Health, "It's exciting to identify areas that can help more accurately predict risk for auditory impairment and that will help providers understand and make the necessary audiological referrals if increased risk is identified."

"Early identification and remediation of auditory impairment is so critical to keeping development of speech and communication milestones of children with hearing impairment close to that of peers without hearing challenges," she said by email.

"It would be interesting to see the longitudinal study extended through the early childhood period, to see if further impairment develops past the 12-month mark or if there is further resolution of impairment past (that) mark, and if milestones are significantly delayed compared to typically hearing peers or peers with SNHL versus ANSD," she observed.

"I'm not sure that unbound bilirubin is currently part of our standard test battery," she added. "If not, this may help make the need for that clearer, and may direct physicians to use it as a predictor and make necessary referrals for audiological follow-up.

Doing so, she concluded, "benefits both the patient in terms of early identification and remediation, and the physician provider and medical community in terms of keeping medical costs lower by making the most appropriate and timely referrals possible."

SOURCE: http://bit.ly/2xB2R97

Pediatrics 2017.