Final answer:
In the given scenario, a phlebotomist should measure O2 levels first as this is a critical, non-invasive procedure that provides immediate results on the infant's oxygen saturation. Subsequently, blood can be drawn for bilirubin levels, followed by DNA testing and the infant screening card.
Step-by-step explanation:
Order of Drawing Blood Tests
When a phlebotomist receives multiple orders for blood tests, it is essential to prioritize the procedures. In the provided scenario, the orders include an infant screening card, O2 levels, bilirubin, and DNA. It is common practice to measure O2 levels first, especially in infants, since this is a non-invasive procedure that can give immediate results regarding the oxygen saturation of the blood, which is critical information. Subsequently, bilirubin levels are often measured through blood to assess liver function and risk of jaundice. Drawing blood for DNA and the screening card can follow as these are not typically dependent on immediate physiological variations.