If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
This month’s stumper
A 3-day-old infant is brought to the office because of yellowing of the skin. He was born to a 28-year-old woman via normal spontaneous vaginal delivery; he was born at 39 weeks and the mother's prenatal labs were all within normal limits. Her blood type is O positive. The patient was discharged after a 2-day stay in the nursery. The patient is breastfed every 2 hours, is not irritable, and eating/stooling well.
Vital signs show temperature 36.9°C (98.5°F), blood pressure 100/60 mmHg, pulse 130/min, and respiratory rate 27/min. On physical examination the patient is significant for slight yellowing of the skin up to the chest with no scleral icterus. The rest of the exams, including fontanelles, red reflex, and abdominal exam, are within normal limits. A heel stick shows a total bilirubin level of 19 mg/dL.
Which of the following is the most appropriate treatment for this patient?
A. Discontinue breastfeeding.
B. Give phototherapy.
C. Place the baby in the sun.
D. Reevaluate the bilirubin level in one day.
E. Reevaluate the bilirubin level in two days.
The correct answer is B.
Kaplan Medical explains why
The patient is a 3-day-old infant who has hyperbilirubinemia. Patients who are 3-days-old (or 72 hours) should have a bilirubin level less than 18 mg/dL regardless of the risk factors. Risk factors for hyperbilirubinemia include:
- ABO incompatibility.
- Jaundice in the first 24 hours.
- Gestational age of 35ndash36 weeks.
- Breastfeeding with inadequate intake.
- Cephalohematoma.
Treatment of hyperbilirubinemia is based on the total bilirubin level and age of the newborn in hours. A nomogram is used to determine the risk of the fetus having hyperbilirubinemia. However, phototherapy is indicated in a low risk fetus (one with no risk factors) when the bilirubin level is greater than 12 mg/dL at 24 hours old, greater than 15 mg/dL at 48 hours old, and greater than 18 mg/dL at 72 hours old.
Why the other answers are wrong
Choice A: Discontinuation of breastfeeding is not indicated. Infants who are jaundiced, breastfeeding exclusively, and have excessive weight loss and signs of dehydration should undergo supplementation with formula. Patients should not stop breastfeeding but rather have supplementation with formula.
Choice C: Placing the baby in the sun is incorrect. Although patients may receive enough irradiance from the sun to reduce the bilirubin a little, the dangers of sunburn outweigh the benefits.
Choices D and E: Patients with severe hyperbilirubinemia will not receive enough irradiance to significantly lower total bilirubin levels. Reevaluating the bilirubin levels in one or two days are both incorrect. This baby has a high bilirubin level based on age. The most feared complication of hyperbilirubinemia is kernicterus, permanent sequelae of hyperbilirubinemia. Patients will develop neurological manifestations at a level of greater than 25 mg/dL. Patients with an already elevated bilirubin should undergo therapy, not wait to reevaluate the level.
Tips to remember
- Newborns with jaundice should have their total bilirubin levels checked.
- Patients with no risk factors and a level of greater than 12 mg/dL at 24 hours old, greater than 15 mg/dL at 48 hours old, and greater than 18 mg/dL at 72 hours old should undergo phototherapy.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
The AMA and Kaplan have teamed up to support you in reaching your goal of passing the USMLE® or COMLEX-USA®. If you're looking for additional resources, Kaplan provides free access to tools for pre-clinical studies, including Kaplan’s Lecture Notes series, Integrated Vignettes, Shelf Prep and more.
