NEONATAL JAUNDICE LAB STUDIES
Category: Child Health
Abstract : neonatal jaundice lab studies: • Bilirubin o Transcutaneous
bilirubinometry can be performed using handheld devices that incorporate
sophisticated optical algorithms to filter out most of the unreflected light
from the bilirubin molecules. o In infants with mild jaundice, transcutaneous
bilirubinometry may be all that is needed to assure that total bilirubin levels
are saf
neonatal jaundice lab studies:
• Bilirubin
o Transcutaneous
bilirubinometry can be performed using handheld devices that incorporate
sophisticated optical algorithms to filter out most of the unreflected light
from the bilirubin molecules.
o In infants with mild jaundice, transcutaneous
bilirubinometry may be all that is needed to assure that total bilirubin levels
are safely below those requiring intervention.
o In infants with moderate
jaundice, transcutaneous bilirubinometry may be useful in selecting patients who
require phlebotomy for serum bilirubin measurement.
o Usually, a total serum
bilirubin level is the only testing required in a moderately jaundiced infant
who presents on the typical second or third day of life without a history and
physical findings suggestive of a pathologic process.
• Additional
studies may be indicated in the following situations:
o Infants who present
with jaundice on the first or after the third day of life
o Infants who are
anemic at birth
o Infants who otherwise appear ill o Infants in whom serum
bilirubin levels are very elevated
o Infants in whom significant jaundice
persists beyond the first 2 weeks of life
o Infants in whom family, maternal,
pregnancy, or case histories suggest the possibility of a pathologic
process
o Infants in whom physical examination reveals findings not explained
by simple physiologic hyperbilirubinemia
• In addition to total serum
bilirubin levels, other suggested studies may include the following:
o Blood
type and Rh determination in mother and infant
o Direct Coombs testing in the
infant
o Hemoglobin and hematocrit values
o Serum albumin levels: This may
be a useful adjunct in evaluating risk of toxicity levels, since albumin binds
bilirubin in a ratio of 1:1 at the primary high-affinity binding site.
o
Nomogram for hour-specific bilirubin values: This may be a useful tool for
predicting, either before or at the time of hospital discharge, which infants
are likely to develop high serum bilirubin values. These infants require close
follow-up monitoring and repeated bilirubin measurements. The predictive ability
has been shown both for bilirubin values measured in serum and for values
measured transcutaneously.
o Measurement of end-tidal carbon monoxide in
breath (ETCO): ETCO may be used as an index of bilirubin production. Measurement
of ETCO may assist in identifying individuals with increased bilirubin
production and, thus, at increased risk of developing high bilirubin levels. An
apparatus has been developed that makes measuring ETCO simple (CO-Stat End Tidal
Breath Analyzer, Natus Medical Inc).
o Peripheral blood film for erythrocyte
morphology
o Reticulocyte count
o Conjugated bilirubin: Note that direct
bilirubin measurements are often inaccurate, are subject to significant
interlaboratory and intralaboratory variation, and generally are not a sensitive
tool for diagnosing cholestasis.
o Liver function tests: Aspartate
aminotransferase (ASAT or SGOT) and alanine aminotransferase (ALAT or SGPT)
levels are elevated in hepatocellular disease. Alkaline phosphatase and
γ-glutamyltransferase (GGT) levels often are elevated in cholestatic disease. A
GGT/ALAT ratio greater than 1 is strongly suggestive of biliary
obstruction.
o Tests for viral and/or parasitic infection may be indicated in
infants with hepatosplenomegaly or evidence of hepatocellular disease.
o
Reducing substance in urine is a useful screening test for galactosemia,
provided the infant has received sufficient quantities of milk.
o Blood gas
measurements: The risk of bilirubin CNS toxicity is increased in acidosis,
particularly respiratory acidosis.
o Bilirubin-binding tests: Although they
are interesting research tools, these tests have not found widespread use in
clinical practice. Although elevated levels of unbound bilirubin are associated
with an increased risk of bilirubin encephalopathy, unbound bilirubin is but one
of several factors that mediate/modulate bilirubin toxicity.
o Thyroid
function tests
Imaging Studies (neonatal jaundices):
• Ultrasound:
Ultrasound examination of the liver and bile ducts is warranted in infants with
laboratory and/or clinical signs of cholestatic disease.
• Radionuclide
scanning: A radionuclide liver scan for uptake of hepatoiminodiacetic acid
(HIDA) is indicated if extrahepatic biliary atresia is suspected. At the
author's institution, patients are pretreated with phenobarbital 5 mg/kg/d for
3-4 days before performing the scan.
Other Tests (neonatal
jaundice):
• Auditory and visual evoked potentials are affected during
ongoing significant jaundice; however, no criteria have been established that
allow extrapolation from evoked potential findings to risk of bilirubin
encephalopathy. Brainstem auditory evoked potentials should be obtained in the
aftermath of severe neonatal jaundice to exclude sensorineural hearing
loss.
• Crying characteristics are changed in significant neonatal
jaundice; however, computerized crying analyses are not used in clinical
practice.
Histologic Findings: Organs, including the brain, are yellow in
any individual with significant jaundice; however, the yellow color is not
evidence of toxicity. This distinction was not always clearly understood in
older descriptions of low-bilirubin kernicterus. In the present, this has
contributed to confusion and uncertainty regarding therapeutic guidelines and
intervention levels.
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