What is a critical lab test that should be drawn for an infant presenting with jaundice?

A critical lab test for an infant presenting with jaundice is the total serum bilirubin test. This test measures the level of bilirubin in the blood, an important diagnostic tool for understanding the extent of jaundice. In infants, elevated bilirubin levels can indicate a variety of conditions, such as physiological jaundice, hemolytic disease, or liver dysfunction.

Determining the total serum bilirubin is essential because it helps healthcare providers assess whether the jaundice is based on unconjugated (indirect) or conjugated (direct) bilirubin levels. This differentiation is crucial for establishing an appropriate and effective treatment plan. For instance, high levels of unconjugated bilirubin suggest hemolysis or other conditions affecting bilirubin metabolism, while high conjugated levels could indicate potential liver or biliary tract problems.

While other tests, such as a complete blood count or hematocrit, can provide valuable information about the infant’s general health or potential causes of jaundice (like anemia), they do not specifically address bilirubin levels. The blood glucose level can be important in certain clinical scenarios but is not directly relevant to the assessment of jaundice. Therefore, the total serum bilirubin test is the most critical and relevant initial step in evaluating jau