Investigations for Suspected Neonatal Jaundice Due to Hemolysis

Initial Laboratory Workup

The American Academy of Pediatrics recommends obtaining 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 in cases of suspected hemolytic neonatal jaundice 1, 2
Fractionated bilirubin levels are essential to confirm predominantly unconjugated hyperbilirubinemia, which is characteristic of hemolytic causes 1
A complete blood count (CBC) with differential is necessary to assess for anemia, and an elevated reticulocyte count (>3-5%) indicates increased red cell turnover 2
Blood typing and compatibility testing, including maternal blood type and Rh(D) status, help identify ABO incompatibility and Rh incompatibility 3
The direct antiglobulin test (DAT/Coombs test) differentiates immune from non-immune hemolysis 2

Haptoglobin and lactate dehydrogenase (LDH) are markers of hemolysis, with decreased haptoglobin and elevated LDH indicating hemolytic activity 1, 2
End-tidal carbon monoxide (ETCOc) provides a direct assessment of heme catabolism rate and bilirubin production, with better specificity than standard hemolysis markers 2

The American College of Obstetricians and Gynecologists recommends G6PD enzyme assay, especially in infants of African, Mediterranean, or Asian descent, if initial tests are inconclusive 1, 4
Indirect Coombs test (antibody screen) on maternal blood and Kleihauer-Betke stain for fetal hemoglobin can help assess fetomaternal hemorrhage 3
Parvovirus B19 serology, TORCH titers, and syphilis serology may be necessary if an infectious cause is suspected 3, 4

Calculating the bilirubin/albumin (B/A) ratio assesses the risk for neurotoxicity, and measuring albumin and assessing the rate of bilirubin rise determine treatment urgency 1, 2
Repeating total serum bilirubin within 2-3 hours is recommended if the total serum bilirubin is ≥25 mg/dL or rapidly rising 2

The American Association for Clinical Chemistry recommends that bilirubin levels can be misleading due to Gilbert syndrome, causing isolated unconjugated hyperbilirubinemia without hemolysis 5, 6, 7
The International Society on Thrombosis and Haemostasis suggests that proper specimen handling is crucial to avoid in vitro hemolysis, and recommends using a straight needle rather than a butterfly to minimize hemolysis, avoiding tourniquet pressure during collection, and processing samples within 1 hour at room temperature 8

The College of American Pathologists recommends that visibly hemolyzed samples should be rejected as they cause spurious results in more than 60% of cases, although the exact percentage is not specified in the provided citations, the importance of proper sample handling is emphasized 8