Neonatal Jaundice Monitoring Levels
Total serum bilirubin (TSB) levels should be checked for neonatal jaundice based on hour-specific nomograms, with particular attention to TSB levels that fall in the high-risk zone (>95th percentile) or high intermediate-risk zone on the Bhutani nomogram. 1
Risk Assessment and Monitoring Thresholds
Pre-discharge Assessment
- Every newborn should undergo risk assessment for developing severe hyperbilirubinemia before discharge 1
- Two recommended clinical options (can be used individually or in combination):
- Predischarge measurement of bilirubin level using TSB or transcutaneous bilirubin (TcB)
- Assessment of clinical risk factors
Risk Zones on Bhutani Nomogram
The hour-specific serum bilirubin values fall into these risk zones:
- High-risk zone (>95th percentile): 39.5% of these infants develop significant hyperbilirubinemia 1
- High intermediate-risk zone: 12.9% develop significant hyperbilirubinemia
- Low intermediate-risk zone: 2.26% develop significant hyperbilirubinemia
- Low-risk zone: 0% develop significant hyperbilirubinemia
Follow-up Testing Intervals
For infants with elevated bilirubin, repeat TSB measurements should be performed at these intervals 2:
- Within 2-3 hours if TSB ≥ 25 mg/dL (428 μmol/L)
- Within 3-4 hours if TSB 20-25 mg/dL (342-428 μmol/L)
- Within 4-6 hours if TSB < 20 mg/dL (342 μmol/L)
Essential Laboratory Tests
Initial Evaluation
For jaundiced infants, the following tests should be performed 1, 2:
- Total and direct (conjugated) bilirubin levels
- Blood type of both infant and mother
- Direct Coombs' test
- Complete blood count with differential and smear
- Reticulocyte count
- Serum albumin level (in selected cases)
Additional Testing for Specific Scenarios
- G6PD testing for infants with significant hyperbilirubinemia, especially those of African American descent (11-13% have G6PD deficiency) 1
- Direct bilirubin measurement if jaundice is prolonged (>2 weeks) 1
- If direct bilirubin is elevated (>1.0 mg/dL when TSB is ≤5 mg/dL), evaluate for causes of cholestasis 1
Risk Factors for Severe Hyperbilirubinemia
Major Risk Factors
- Predischarge TSB or TcB level in the high-risk zone
- Jaundice observed in the first 24 hours
- Blood group incompatibility with positive direct antiglobulin test
- Gestational age 35-36 weeks
- Previous sibling received phototherapy
- Cephalohematoma or significant bruising
- Exclusive breastfeeding with poor intake or excessive weight loss
- East Asian race
Minor Risk Factors
- Predischarge TSB or TcB in high intermediate-risk zone
- Gestational age 37-38 weeks
- Jaundice observed before discharge
- Previous sibling with jaundice
- Macrosomic infant of diabetic mother
- Maternal age >25 years
- Male gender
Practical Considerations
Capillary vs. Venous Samples
- Most published data relating TSB levels to kernicterus are based on capillary blood TSB levels 1
- Obtaining a venous sample to "confirm" an elevated capillary TSB is not recommended as it delays treatment 1
Transcutaneous Bilirubin Measurement
- TcB can be used as a screening tool to identify the need for blood sampling 3
- TcB tends to underestimate TSB by approximately 0.7 mg/dL 3
- TcB is particularly useful before early discharge or for home visits 4
Common Pitfalls to Avoid
- Delaying treatment to confirm capillary TSB with venous sampling
- Failing to assess risk factors in addition to TSB levels
- Not recognizing G6PD deficiency, which requires intervention at lower TSB levels 1
- Inadequate follow-up, particularly for infants discharged before 72 hours of age
- Misinterpreting direct bilirubin results (laboratory measurement is not precise) 1
Remember that while most jaundiced term infants have no underlying illness, careful monitoring of TSB levels according to risk factors is essential to prevent kernicterus and other complications of severe hyperbilirubinemia.