What blood work is recommended for a neonate presenting with jaundice?

Blood Work for Neonatal Jaundice

For any jaundiced neonate, immediately obtain total serum bilirubin (TSB) or transcutaneous bilirubin (TcB), and if the mother has not had prenatal blood grouping or is Rh-negative, obtain infant blood type, Rh (D) type, and direct antibody test (Coombs' test) from cord blood. 1, 2

Initial Laboratory Assessment Based on Timing and Severity

Jaundice in First 24 Hours (Always Pathologic)

• Obtain TSB or TcB immediately - visual assessment is unreliable and dangerous, particularly in darkly pigmented infants 2, 3
• Essential workup includes:
  • Infant blood type and Rh (D) 1, 2
  • Direct antibody test (Coombs' test) 1, 2
  • Complete blood count with peripheral smear 2, 4
  • Reticulocyte count 2, 4
  • G6PD level 2, 4
  • Direct or conjugated bilirubin 2, 4

Maternal Blood Type Considerations

• If mother is Rh-negative or has no prenatal blood grouping: Strongly obtain infant blood type, Rh (D) type, and direct antibody test from cord blood 1
• If mother is blood group O, Rh-positive: Testing cord blood for infant blood type and direct antibody test is optional but not required if appropriate surveillance and follow-up are ensured 1

Laboratory Workup for Rapidly Rising or Elevated Bilirubin

When TSB is Rising Rapidly (Crossing Percentiles) or Infant Requires Phototherapy

• Blood type and direct antibody test (Coombs') 2, 3
• Complete blood count with peripheral smear - examine for red blood cell morphological abnormalities that indicate hemolytic conditions 2, 5
• Direct or conjugated bilirubin 2, 4
• Reticulocyte count 2, 4
• G6PD level - critical in African Americans (11-13% prevalence), Mediterranean, and Asian populations 3

High-Risk Populations Requiring G6PD Testing

• Test for G6PD deficiency when: TSB approaches exchange levels, bilirubin fails to respond to phototherapy, or severe hyperbilirubinemia occurs in at-risk ethnic groups (Greek, Turkish, Sardinian, Nigerian, Sephardic Jewish from Iraq/Iran/Syria/Kurdistan) 3, 6
• Late-rising bilirubin is typical of G6PD deficiency 6

Prolonged Jaundice (Beyond 2-3 Weeks)

Essential Testing for Jaundice Persisting Beyond 3 Weeks

• Measure direct or conjugated bilirubin to rule out cholestatic jaundice and biliary atresia 1, 4, 6
• Verify metabolic screen for hypothyroidism is normal - congenital hypothyroidism causes indirect hyperbilirubinemia 6
• Assess stool and urine color: Pale stools or dark yellow urine indicate cholestasis requiring immediate direct bilirubin measurement 6

Critical Interpretation Principles

Age-Specific Interpretation

• Interpret all bilirubin levels according to infant's age in hours, not days 2, 4, 3
• Use hour-specific nomograms (Bhutani nomogram) to determine risk zone and guide management 3

Common Pitfalls to Avoid

• Never rely on visual assessment alone - it leads to dangerous errors, especially in darkly pigmented infants 2, 3
• Never subtract direct bilirubin from total bilirubin when making phototherapy decisions - use total bilirubin for treatment decisions 2, 4
• Never discharge an infant with jaundice in first 24 hours without objective bilirubin measurement and clear follow-up plan 2, 3
• Never ignore failure to respond to phototherapy - consider unrecognized hemolytic process 6

Risk Stratification Factors That Lower Treatment Thresholds

• Gestational age 35-37 weeks 2, 4
• Hemolytic disease (ABO or Rh incompatibility) 2, 3
• G6PD deficiency 2, 4
• Sepsis 2, 4
• Acidosis 2, 4
• Albumin <3.0 g/dL 2, 4