Which test is used to screen for an inborn error of metabolism in a newborn?

• A. APGAR score
• B. Blood glucose
• C. CBC
• D. PKU screening test

Answer: (D)

Testing newborns for metabolic disorders focuses on identifying inherited conditions that affect how the body processes certain substances. The PKU screening test specifically checks the blood for elevated phenylalanine, which signals phenylketonuria, an inborn metabolic disorder. Detecting it early allows dietary management to prevent serious outcomes, so this test is used as a routine newborn screen. In contrast, the APGAR score is a quick assessment of the baby’s overall condition at birth, not a metabolic test. Checking blood glucose looks for immediate energy problems like hypoglycemia, and a CBC screens for blood cell issues, neither of which target metabolic disorders detected by PKU screening.