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Bacterial Pneumonia (cont.)

What Tests Do Doctors Use to Diagnose Bacterial Pneumonia?

Pneumonia can be diagnosed simply by a doctor listening to the patient's lungs. Certain sounds heard through a stethoscope may indicate infection.

  • One of the easiest tests to perform is pulse oximetry, sometimes called "pulse ox." A probe that looks like a clothespin is gently attached to the patient's finger, toe, or ear. A special light shines through the skin to estimate how much oxygen the patient has in the bloodstream. If the oxygen level is lower than expected, the lungs are not working properly and it may mean the patient has pneumonia.
  • A chest X-ray can help identify which part of the patient's lung is infected. An X-ray also can show abnormal fluid collections which also can help diagnose pneumonia.
  • The patient may have blood drawn. Laboratory tests can show that the immune system is working properly to fight off infection. They also show whether the patient has enough red blood cells to carry oxygen or whether the bacteria is in the bloodstream.
  • Occasionally the doctor may need to sample blood from one of the patient's arteries (usually in the wrist) in order to get an exact measurement of how well the patient is exchanging oxygen and carbon dioxide. This test, called an arterial blood gas ("ABG" or "blood gas"), is very important, takes only a minute, and is done with a very small needle and syringe. This test cannot use the blood sampled from the patient's veins.
  • Sometimes the doctor will collect some of the patient's sputum and view it under a microscope. Certain stains, or dyes, used on the sputum can assist the doctor in diagnosing the bacterium is causing pneumonia. Sputum cultures may also be performed. In these tests, the sputum is put on a plate to help it grow so a laboratory specialist can identify the specific bacteria.
  • If the patient is admitted to the hospital, the doctor will draw blood and send it to the laboratory so that it may also be cultured to determine whether bacteria are present in the bloodstream. There are also urine (urinalysis) and blood tests that examines the patient's immune system response to infection. These can also help determine the cause of the pneumonia.
Medically Reviewed by a Doctor on 6/24/2016

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