What investigations should be done when suspecting Neonatal Jaundice (NNJ) due to hemolysis?

Investigations for Suspected Neonatal Jaundice Due to Hemolysis

When hemolytic neonatal jaundice is suspected, immediately obtain fractionated bilirubin, complete blood count with reticulocyte count, blood typing of both mother and infant, and direct antiglobulin test (Coombs test) to confirm hemolysis and identify the underlying cause. 1, 2, 3

Initial Laboratory Workup

Essential First-Line Tests

• Fractionated bilirubin levels to confirm predominantly unconjugated hyperbilirubinemia, which is characteristic of hemolytic causes 1

• Complete blood count (CBC) with differential to assess for anemia, which typically shows:

  • Lower hemoglobin, erythrocytes, and hematocrit in hemolytic jaundice 4
  • Elevated reticulocyte count (>3-5%), indicating increased red cell turnover 2, 3, 4
  • Peripheral blood smear for red cell morphology abnormalities 2, 3

• Blood typing and compatibility testing:

  • Maternal blood type and Rh(D) status 5
  • Infant blood type 3, 6
  • This identifies ABO incompatibility (most common cause, occurring in 54.4 per 1,000 births) and Rh incompatibility 6, 4

• Direct antiglobulin test (DAT/Coombs test) to differentiate immune from non-immune hemolysis 2, 6

  • Positive DAT indicates immune-mediated hemolysis (ABO/Rh incompatibility) 6
  • 65% of infants with positive DAT develop jaundice versus 35% with negative DAT 6

Additional Hemolysis Markers

• Haptoglobin (decreased in hemolysis) 1, 2
• Lactate dehydrogenase (LDH) (elevated in hemolysis) 1, 2
• End-tidal carbon monoxide (ETCOc) provides direct assessment of heme catabolism rate and bilirubin production, with better specificity than standard hemolysis markers 2

Second-Line Investigations

When Initial Tests Are Inconclusive

• G6PD enzyme assay especially in infants of African, Mediterranean, or Asian descent 1, 7
• Indirect Coombs test (antibody screen) on maternal blood if not previously done or if initially normal 5
• Kleihauer-Betke stain for fetal hemoglobin to assess fetomaternal hemorrhage 5

Infectious Workup (If Indicated)

• Parvovirus B19 serology 5, 7
• TORCH titers (toxoplasmosis, CMV) via polymerase chain reaction studies 5, 7
• Syphilis serology 5

Severity Assessment and Monitoring

• Calculate bilirubin/albumin (B/A) ratio to assess risk for neurotoxicity 2
• Measure albumin and assess rate of bilirubin rise to determine treatment urgency 1, 2
• Repeat total serum bilirubin within 2-3 hours if TSB ≥25 mg/dL or rapidly rising 2

Common Pitfalls to Avoid

• Failing to fractionate bilirubin: This is essential for confirming unconjugated hyperbilirubinemia characteristic of hemolysis 1
• Relying solely on reticulocyte counts: Nearly threefold differences exist between laboratories due to methodological variations, limiting reliability as a screening test 8
• Overlooking negative DAT results: Approximately 35% of ABO hemolytic disease cases have negative direct antiglobulin tests but still develop significant jaundice 6
• Delaying G6PD testing in at-risk populations: This enzyme deficiency is easily missed without specific testing 1, 7
• Ignoring the clinical context: Leukocytosis may indicate concurrent septicemia, which can coexist with or mimic hemolytic jaundice 3

Diagnostic Algorithm Summary

1. Obtain fractionated bilirubin to confirm unconjugated hyperbilirubinemia 1
2. Perform CBC with reticulocyte count and peripheral smear 2, 3
3. Check maternal and infant blood types with DAT 5, 6
4. Add hemolysis markers (haptoglobin, LDH, or ETCOc if available) 1, 2
5. If immune causes excluded, test for G6PD deficiency and consider infectious workup 1, 7
6. Calculate B/A ratio and monitor bilirubin trends to guide treatment intensity 2