Question

A six-month old female is brought to the clinic in December with wheezing and respiratory difficulty for the past several hours. She did have a low-grade fever two days ago accompanied by rhinorrhea, but has otherwise been well since birth. Vital signs are temperature 38.6 C (101.5 F), pulse 160, blood pressure 87/59, respirations 60/min. Nasal flaring and intercostal retractions are noted. Auscultation of the lungs reveals faint inspiratory crackles at the lung bases and diffuse expiratory wheezing. A chest x-ray shows a normal cardiac silhouette, hyperexpanded lungs, and peribronchial thickening. Which of the following tests would be most likely to confirm the diagnosis in this patient?

A. Rigid bronchoscopy
B. EKG
C. Methacholine challenge test
D. Rapid antigen test for RSV
E. Sweat chloride test

Answer 1

The most likely diagnosis for the six-month-old female with respiratory symptoms is bronchiolitis caused by RSV, and the rapid antigen test for RSV is the most suitable test to confirm this diagnosis.

Step-by-step explanation:

The clinical presentation described in the question is typical of a viral respiratory infection in infants, and based on the described symptoms such as wheezing, respiratory difficulty, fever, and findings of hyperexpanded lungs and peribronchial thickening on the chest x-ray, the most likely diagnosis is bronchiolitis, commonly caused by the Respiratory Syncytial Virus (RSV). The best test to confirm this diagnosis would be a rapid antigen test for RSV, which can quickly detect the presence of the virus.

The other tests mentioned have different indications. A rigid bronchoscopy would be more useful in case of suspected airway obstruction by a foreign body. An EKG would be needed if there was a suspicion of heart-related issues. A methacholine challenge test is used to diagnose asthma, typically in older patients who can participate in pulmonary function testing. Lastly, a sweat chloride test is indicative for cystic fibrosis, which does not match the acute onset of symptoms consistent with a viral infection. Therefore, the answer is D. Rapid antigen test for RSV.