Sometimes pneumonia is hard to diagnose because it may cause symptoms commonly seen in people with colds or the flu. You may not realize it's more serious until it lasts longer than these other conditions. Your doctor will diagnose pneumonia based on your medical history, a physical exam, and test results. Your doctor may be able to diagnose you with a certain type of pneumonia based on how you got your infection and the type of germ causing your infection.
Your doctor will ask about your signs and symptoms and how and when they began. To find out whether you have bacterial, viral, or fungal pneumonia, your doctor also may ask about:
- Any recent traveling you've done
- Your hobbies
- Your exposure to animals
- Your exposure to sick people at home, school, or work
- Your past and current medical conditions, and whether any have gotten worse recently
- Any medicines you take
- Whether you smoke
- Whether you've had flu or pneumonia vaccinations
Your doctor will listen to your lungs with a stethoscope. If you have pneumonia, your lungs may make crackling, bubbling, and rumbling sounds when you inhale. Your doctor also may hear wheezing. Your doctor may find it hard to hear sounds of breathing in some areas of your chest.
If your doctor thinks you have pneumonia, he or she may recommend one or more of the following tests.
- Chest x ray to look for inflammation in your lungs. A chest x ray is the best test for diagnosing pneumonia. However, this test won't tell your doctor what kind of germ is causing the pneumonia.
- Blood tests such as a complete blood count (CBC) to see if your immune system is actively fighting an infection.
- Blood culture to find out whether you have a bacterial infection that has spread to your bloodstream. If so, your doctor can decide how to treat the infection.
Your doctor may recommend other tests if you're in the hospital, have serious symptoms, are older, or have other health problems.
- Sputum test. Your doctor may collect a sample of sputum (spit) or phlegm (slimy substance from deep in your lungs) that was produced from one of your deep coughs and send the sample to the lab for testing. This may help your doctor find out if bacteria are causing your pneumonia. Then, he or she can plan your treatment.
- Chest computed tomography (CT) scan to see how much of your lungs is affected by your condition or to see if you have complications such as lung abscesses or pleural effusions. A CT scan shows more detail than a chest x ray.
- Pleural fluid culture. For this test, a fluid sample is taken from the pleural space (a thin space between two layers of tissue that line the lungs and chest cavity). Doctors use a procedure called thoracentesis to collect the fluid sample. The fluid is studied for bacteria that may cause pneumonia.
- Pulse oximetry. For this test, a small sensor is attached to your finger or ear. The sensor uses light to estimate how much oxygen is in your blood. Pneumonia can keep your lungs from moving enough oxygen into your bloodstream. If you're very sick, your doctor may need to measure the level of oxygen in your blood using a blood sample. The sample is taken from an artery, usually in your wrist. This test is called an arterial blood gas test.
- Bronchoscopy is a procedure used to look inside the lungs' airways. If you're in the hospital and treatment with antibiotics isn't working well, your doctor may use this procedure. Your doctor passes a thin, flexible tube through your nose or mouth, down your throat, and into the airways. The tube has a light and small camera that allow your doctor to see your windpipe and airways and take pictures. Your doctor can see whether something is blocking your airways or whether another factor is contributing to your pneumonia. Your doctor may use this procedure to collect samples of fluid from the site of pneumonia (called bronchoalveolar lavage or BAL) or to take small biopsies of lung tissue to help find the cause of your pneumonia.
Types of pneumonia
Your doctor may also diagnosis you with a certain type of pneumonia. Pneumonia is named for the way in which a person gets the infection or for the germ that causes the infection.
- Community-Acquired Pneumonia (CAP). CAP is the most common type of pneumonia and is usually caused by pneumococcus bacteria. Most cases occur during the winter. CAP occurs outside of hospitals and other health care settings. Most people get CAP by breathing in germs (especially while sleeping) that live in the mouth, nose, or throat.
- Hospital-Acquired Pneumonia (HAP). HAP is when people catch pneumonia during a hospital stay for another illness. HAP tends to be more serious than CAP because you're already sick. Also, hospitals tend to have more germs that are resistant to antibiotics that are used to treat bacterial pneumonia.
- Ventilator-associated pneumonia (VAP). VAP is when people who are on a ventilator machine to help them breathe get pneumonia.
- Atypical pneumonia. Atypical pneumonia is a type of CAP. It is caused by lung infections with less common bacteria than the pneumococcus bacteria that cause CAP. Atypical bacteria include Legionella pneumophila, Mycoplasma pneumoniae, or Chlamydia pneumoniae.
- Aspiration pneumonia. This type of pneumonia can occur if you inhale food, drink, vomit, or saliva from your mouth into your lungs. This may happen if something disturbs your normal gag reflex, such as a brain injury, swallowing problem, or excessive use of alcohol or drugs. Aspiration pneumonia can cause lung abscesses.