The nurse is caring for a patient with pneumonia. Which laboratory test would best help the nurse to monitor the condition of this patient?

A. White blood cell (WBC) count, arterial blood gases (ABGs): WBC count helps assess the presence and severity of infection, while ABGs evaluate the patient’s oxygenation and gas exchange critical factors in pneumonia. These tests directly reflect respiratory function and the inflammatory response. B. Complete blood count (CBC), urinalysis: While a CBC includes the WBC count, the rest of the values are not directly helpful in tracking pneumonia progression. A urinalysis assesses kidney and urinary tract health, not respiratory infection, so it is not essential. C. Electrolytes, serum creatinine: These tests provide information on renal function and electrolyte balance, which may be relevant in complex cases but are not specific indicators of pneumonia status or treatment response. D. Partial thromboplastin time (PTT), serum potassium: PTT evaluates clotting, and serum potassium assesses electrolyte balance. Neither test provides useful information about the progression or resolution of pneumonia.