To evaluate the effectiveness of an antibiotic prescribed for a respiratory tract infection, which laboratory value should be monitored?

• A. Sputum culture and sensitivity
• B. White blood cell count
• C. Hemoglobin
• D. Blood urea nitrogen

Answer: (B)

Tracking how well an antibiotic is working for a respiratory infection centers on the body's inflammatory response to infection. White blood cell count is a practical marker because infections commonly raise WBCs, especially neutrophils. When the antibiotic effectively combats the bacteria, the infection eases and the WBC count tends to return toward normal, indicating improvement. A sputum culture and sensitivity is useful for choosing the right antibiotic initially, but it doesn’t reliably show how the patient is responding once treatment has started. Hemoglobin and blood urea nitrogen aren’t direct indicators of infection control or antibiotic effectiveness and can be influenced by other factors. So, monitoring the white blood cell count provides the most direct clue about whether the infection is resolving with the prescribed antibiotic.