A 1-month-old male infant is brought to the emergency depart…
A 1-month-old male infant is brought to the emergency department because he has been having seizures for the past 30 minutes The mother has a history of alcohol use while she was pregnant with the patient. Physical examination shows hypertelorism, shortened philtrum, and low-set ears. Laboratory studies show hypocalcemia and hyperphosphatemia. Chest x-ray study shows absence of a thymic shadow. After stabilizing the patient’s condition and before discharge, which of the following is the most appropriate screening test?