What should be measured in a newborn who presents with hyperbilirubinemia –
**Core Concept**
Hyperbilirubinemia in newborns is a condition characterized by elevated levels of bilirubin in the blood, which can lead to kernicterus if left untreated. The goal of assessment is to determine the underlying cause of hyperbilirubinemia and to predict the risk of developing bilirubin encephalopathy.
**Why the Correct Answer is Right**
To assess the risk of bilirubin encephalopathy, healthcare providers measure the total serum bilirubin (TSB) level along with the age of the newborn. This is because the risk of kernicterus increases exponentially with bilirubin levels above 15 mg/dL in the first week of life. The Kernicterus risk can be assessed using the Sarnat and Sarnat staging system or the Bhutani nomogram. The TSB level is used in conjunction with the age of the newborn to calculate the risk of bilirubin encephalopathy.
**Why Each Wrong Option is Incorrect**
**Option A:** Bilirubin binding capacity (BC) - While BC is an important measurement in assessing the binding capacity of albumin to bilirubin, it is not the primary measurement used to assess the risk of bilirubin encephalopathy in newborns.
**Option B:** Direct bilirubin - Direct bilirubin levels are not the primary measurement used to assess the risk of bilirubin encephalopathy in newborns. However, direct bilirubin levels are useful in differentiating between pre-hepatic and post-hepatic causes of jaundice.
**Option C:** Indirect bilirubin - Indirect bilirubin levels are not the primary measurement used to assess the risk of bilirubin encephalopathy in newborns. However, indirect bilirubin levels are useful in assessing the degree of unconjugated hyperbilirubinemia.
**Option D:** Hematocrit - Hematocrit is not a primary measurement used to assess the risk of bilirubin encephalopathy in newborns. However, hematocrit levels can be useful in assessing the degree of polycythemia or anemia.
**Clinical Pearl / High-Yield Fact**
The American Academy of Pediatrics recommends that all newborns be assessed for jaundice at 24-48 hours of age and that bilirubin levels be measured in newborns with jaundice to assess the risk of bilirubin encephalopathy.
**Correct Answer:** A. Total serum bilirubin (TSB) level.