What is a sputum test?

A sputum test, also known as a sputum culture, is a test that your doctor may order when you have a respiratory tract infection or other lung-related disorder to determine what is growing in the lungs.

Sputum is a thick substance that accumulates when bacteria or fungi grows and multiples in the lungs or bronchi. As it accumulates, the growing substance can make breathing more difficult and cause coughing.

A sputum test can diagnose:

  • Bronchitis
  • Lung abscess
  • Pneumonia
  • Tuberculosis
  • Chronic obstructive pulmonary disease
  • Cystic fibrosis

Who needs a sputum test?

Bacteria, viruses and fungi can cause respiratory conditions. By understanding the cause of your symptoms, your doctor can more effectively treat your condition.

If you have any of the following symptoms, you may need a sputum test:

  • Cough
  • Fever
  • Chills
  • Fatigue
  • Muscle aches
  • Breathing problems
  • Chest pain
  • Confusion

What are the side effects associated with a sputum test?

Although there are not any major side effects associated with having a sputum culture, deep coughing can cause some minor discomfort. You may also feel light chest pain after giving a sample.

Patients who have had previous abdominal surgery may need to hold a pillow over their stomach to minimize discomfort.

What to expect during a sputum test?

During a sputum test, you will be asked to cough deeply enough to bring up a large quantity of sputum so your doctor can evaluate it. The most challenging part of the test is to produce a sample size large enough for it to be tested. Saliva that lives in the upper airways is not useful for this test.

Your doctor will evaluate the color of your sample to understand what may be going on with you.

  • Off-white, yellow or green sputum can indicate you have pneumonia or bronchitis
  • Red or rusty can indicate you have a more serious condition that needs more testing
  • Grey or back can indicate that you are a smoker or someone who works in a sooty place (like a coal mine)

Results from a sputum test

Your sputum sample will be sent to a laboratory within one to hours of production. A pathologist will run tests to determine if the growth is a bacterium, virus or fungus. There are some bacteria in the lungs that grow naturally, so it is important to determine what is making you sick and what bacteria are healthy.

Your pathologist will send a report to your doctor as soon as possible. Typically, your doctor will have test results back within a few days. Rapid TB tests can be ready in as little as 24 hours, but results for other lung diseases can take as long as eight weeks.

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