Kaplan USMLE Step 1: What drug could have likely prevented infant's condition?

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 1 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.

A 10-month-old infant is brought to the emergency department in early December after many children in his daycare become ill with high fever, runny nose, cough, wheezing, and loss of appetite, with two cases requiring hospitalization. He has a history of prematurity and was born at 29 weeks' gestation. He also has a history of chronic lung disease due to premature lungs and required oxygen until he was 4 months of age. His temperature is 38°C (100.4°F), pulse is 113/min, respirations are 28/min, and oxygen saturation is 88% on room air. He is placed on 2L nasal cannula and saturations improve to 96%. Physical examination shows a small infant in no acute distress with wheezing bilaterally on auscultation. The infant has a significant amount of purulent nasal secretions. Laboratory studies show:

White blood cell count: 15,500/mm³

Neutrophils: 40%

Lymphocytes: 45%

Bands:7%

Monocytes: 8%

Hemoglobin: 11.4 g/dL

Hematocrit: 33.4 %

Platelets: 390,000m³

Rapid RSV: Positive

Rapid influenza: Negative

Which of the following drugs could most likely have prevented this patient's condition?

A. Abatacept

B. Infliximab

C. Palivizumab

D. Prednisone

E. Zanamivir

The correct answer is C.

Palivizumab is a monoclonal antibody that exhibits neutralizing and fusion-inhibitory activity against RSV. It is indicated for RSV prophylaxis in high-risk infants <24 months old, such as those with a past history of chronic lung disease requiring oxygen for a prolonged period of time, those with severe prematurity, or those with congenital heart disease.

Choice A: The patient has a respiratory syncytial virus (RSV) infection which could have been prevented with the monoclonal antibody palivizumab. Abatacept is used in the management of autoimmune diseases such as rheumatoid arthritis.