Other tests for lung infections, such as pneumonia and acute bronchitis, may include:

• Blood tests or cultures. Blood tests may help tell if you have antibodies to a specific organism that can cause pneumonia or if you have a specific virus, such as influenza (flu) or respiratory syncytial virus (RSV). Doctors can use blood cultures to test for bacteria in your bloodstream.
• Oximetry. An oximeter can estimate the amount of oxygen in your blood. A sensor in a cuff or clip is placed on the end of your finger. This sensor measures how much oxygen is in your blood. The oximeter machine shows the result.
• Arterial blood gases. This test can measure the levels of oxygen in a sample of blood drawn from your artery. Doctors use this test to find out whether enough oxygen is getting into your bloodstream from your lungs.
• Bronchoscopy. This is a visual exam of the tubes leading to your lungs. This test is usually done by a pulmonologist (lung specialist). The doctor inserts a small, lighted device through your nose or mouth into the tubes leading to your lungs. During the procedure, the doctor can obtain samples of tissue, fluid, or mucus.
• Lung biopsy. This test is done on a very small piece of lung tissue. It looks for conditions such as lung cancer or fibrous tissue in the lungs (pulmonary fibrosis). Your doctor obtains lung tissue by inserting a needle into your chest between two ribs or by using bronchoscopy.
• Thoracentesis. This test involves puncturing the chest wall to obtain fluid from the space around the lungs. Fluid obtained during the test can be checked for signs of infection or cancer.
• Computed tomography (CT) scan. A CT scan uses X-rays to produce detailed pictures of structures inside your body. It may be used in people who aren't responding to their treatment.