From the Guidelines
For a neonate being admitted with hyperbilirubinemia, you should order total and direct (conjugated) bilirubin levels, complete blood count with peripheral smear, blood type and Rh factor for both baby and mother, direct Coombs test, reticulocyte count, glucose-6-phosphate dehydrogenase (G6PD) screening, and serum albumin. These initial labs help determine the cause and severity of jaundice, as recommended by the American Academy of Pediatrics 1. Total bilirubin quantifies the overall level while direct bilirubin helps distinguish between conjugated and unconjugated hyperbilirubinemia. CBC with peripheral smear can identify hemolysis, infection, or blood disorders. Blood typing and Coombs testing detect ABO or Rh incompatibility that may cause hemolytic disease. Reticulocyte count helps assess red blood cell production and turnover. G6PD screening is important as deficiency can cause severe hemolysis, especially with certain medications or foods, and is crucial in infants with significant hyperbilirubinemia 1. Serum albumin is useful because albumin binds bilirubin, and low levels may increase risk of kernicterus.
Consider adding liver function tests, blood cultures, and thyroid studies if there are concerns about other underlying conditions, as suggested by the guidelines for laboratory evaluation of the jaundiced infant 1. These labs should be ordered promptly as treatment decisions depend on identifying the cause and assessing the risk of bilirubin encephalopathy. The risk of bilirubin encephalopathy can be estimated using the risk zone as a predictor of hyperbilirubinemia, as shown in Table 4 of the study by 1.
Key points to consider when ordering initial labs for a neonate with hyperbilirubinemia include:
- Measuring total and direct bilirubin levels to quantify the overall level and distinguish between conjugated and unconjugated hyperbilirubinemia
- Ordering a complete blood count with peripheral smear to identify hemolysis, infection, or blood disorders
- Performing blood typing and Coombs testing to detect ABO or Rh incompatibility
- Assessing red blood cell production and turnover with a reticulocyte count
- Screening for G6PD deficiency, especially in infants with significant hyperbilirubinemia
- Measuring serum albumin to assess the risk of kernicterus
- Considering additional tests, such as liver function tests, blood cultures, and thyroid studies, if there are concerns about other underlying conditions, as recommended by 1.
From the Research
Initial Labs for Neonatal Hyperbilirubinemia
When a neonate is admitted for hyperbilirubinemia, the following initial labs should be considered:
- Complete Blood Count (CBC) to evaluate for hemolysis or infection
- Blood type and Rh factor to assess for isoimmune hemolytic disease
- Direct and indirect bilirubin levels to determine the severity of hyperbilirubinemia
- Liver function tests (LFTs) to evaluate for liver dysfunction
- Thyroid function tests to rule out hypothyroidism as a cause of hyperbilirubinemia
Rationale for Lab Tests
The rationale for these lab tests is based on the potential causes and complications of hyperbilirubinemia in neonates, as discussed in several studies 2, 3, 4, 5, 6. For example, hemolysis and isoimmune hemolytic disease can cause severe hyperbilirubinemia, while liver dysfunction and hypothyroidism can contribute to elevated bilirubin levels.
Additional Considerations
Additional lab tests may be considered based on the individual patient's risk factors and clinical presentation, such as:
- Screening for infections, such as sepsis or urinary tract infections
- Evaluation for genetic disorders, such as glucose-6-phosphate dehydrogenase (G6PD) deficiency
- Assessment for other underlying medical conditions that may contribute to hyperbilirubinemia
It is essential to note that the specific lab tests ordered may vary depending on the patient's individual needs and the clinical judgment of the healthcare provider, as guided by evidence-based recommendations 5, 6.