**Question:** A 64 year old man presents to the physician's office complaining of fevers for the past 2 days. Over the past 24 hours, he has developed a productive cough. He also reports frequent chills, and has been waking for the past 2 nights with drenching sweats. His past medical history is remarkable only for mild essential hypertension. On physical examination, he does not appear chronically ill but appears moderately dyspneic. His temperature is 38.6°C (101.4°F), blood pressure is 136/94 mmHg, and respirations are 26/min. There is no jugular venous distention. The lungs have coarse rhonchi at the right lung base with increased fremitus in the same area. He has a regular heart rhythm, with a 1/6 systolic murmur at the left sternal border. The remainder of the physical examination is unremarkable. Which of the following is the most appropriate next step in diagnosis?

A. Perform a chest X-ray
B. Order a complete blood count (CBC)
C. Request a sputum culture and sensitivity test
D. Begin treatment for community-acquired pneumonia

**Correct Answer:**

A. Perform a chest X-ray

**Core Concept:**

The patient presents with symptoms and signs consistent with pneumonia, which is a respiratory infection that causes inflammation of the air sacs (alveoli) in one or both lungs. The patient exhibits clinical findings such as fever, cough, dyspnea, and crackles (coarse rhonchi) on auscultation, which are indicative of pneumonia.

**Why the Correct Answer is Right:**

Given the patient's symptoms and signs, the most appropriate next step in diagnosis would be to perform a chest X-ray (option A) as it is a non-invasive imaging test that can provide valuable information regarding the extent and distribution of the pneumonia. Chest X-ray can reveal the presence and location of lung infiltrates, which are areas of increased density in the lungs. These infiltrates can indicate pneumonia.

**Why Other Options are Incorrect:**

Option B (Order a complete blood count - CBC) is irrelevant as it only provides information about the patient's blood parameters, like red blood cell count, hemoglobin, and platelet count, without providing any information about the lung infection.

Option C (Request a sputum culture and sensitivity test) might be considered but chest X-ray is a more direct and rapid way to diagnose pneumonia, particularly when the patient's symptoms and signs are indicative of pneumonia.

Option D (Begin treatment for community-acquired pneumonia) is not the best first step as the diagnosis should precede treatment initiation. Chest X-ray allows for a definitive diagnosis, and then appropriate antibiotics can be prescribed based on the results.