In evaluating COPD/asthma, which test is typically performed only if infection is suspected?

• A. Pulse Ox
• B. CXR
• C. Sputum culture (if infection suspected)
• D. ABG/VBG

Answer: (C)

The key idea is that some tests are routine parts of evaluating COPD or asthma, while others are specifically used when an infectious process is suspected. A sputum culture falls into the latter category: you order it only when there are signs of infection (such as fever, purulent sputum, increased white blood cells, or a clinical scenario suggesting pneumonia or a bacterial exacerbation). Its job is to identify the exact bacterial organism so you can tailor antibiotic therapy appropriately. In contrast, pulse oximetry, chest X-ray, and arterial/venous blood gas testing provide information on oxygenation, lung structure or complications, and gas exchange, and they’re used as part of routine assessment during exacerbations rather than solely for suspected infection.