A sputum test, also known as a sputum culture, to detect and identify bacteria or fungi that infect the lungs or breathing passages is a test that your doctor may order when you have a respiratory tract infection or other lung-related disorder to detect and identify bacteria or fungi that infect the lungs or breathing passages, growing in the lungs. Sputum is a thick substance that accumulates when bacteria or fungi grow and multiply in the lungs or bronchi.

A sputum Gram stain is a laboratory test used to detect bacteria in a sputum sample. Sputum is the material that comes up from your air passages when you cough very deeply.

The Gram stain method is one of the most commonly used methods to rapidly detect a bacterial infection, including pneumonia.

How the Test is Performed

A sputum sample is needed. You will be asked to cough deeply and spit any material that comes up from your lung into a special container.

• If this does not work, you may receive a breathing treatment before the test to help you cough more deeply.
• If you have a dry cough or are unable to produce a sample, a bronchoscopy may be necessary.

The sample is sent to a lab. The lab team member places a very thin layer of the sample onto a glass slide. This is called a smear. Stains are placed on the sample. The lab team member looks at the stained slide under a microscope, checking for bacteria and white blood cells. The color, size, and shape of the cells help identify the bacteria.

How to Prepare for the Test

No preparation is usually needed unless bronchoscopy is necessary.

How the Test Will Feel

How the test will feel depends on the method used to produce the sample. More discomfort is associated with bronchoscopy.

Why the Test is Performed

Your doctor may order this test if you have a persistent or prolonged cough, or if you are coughing up material that has a foul odor or unusual color. The test may also be done if you have other signs and symptoms of respiratory disease or infection.

Normal Results

A normal result means that few to no white blood cells and no bacteria were seen in the sample. The sputum is clear, thin, and odorless.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means that bacteria is seen in the test sample. You may have a bacterial infection. A culture is needed to confirm the diagnosis.

RIsks

There are no risks associated with coughing up a sample. See the article on bronchoscopy for information regarding risks related to that procedure.

Considerations

The test may need to be repeated if the sample contains only saliva from the mouth.

Gram stain

Urethral discharge – Gram stain; Feces – Gram stain; Stool – Gram stain; Joint fluid – Gram stain; Pericardial fluid – Gram stain; Gram stain of urethral discharge; Gram stain of the cervix; Pleural fluid – Gram stain; Sputum – Gram stain; Skin lesion – Gram stain; Gram stain of skin lesion; Gram stain of tissue biopsy

A Gram stain is a test used to identify bacteria. It is one of the most common ways to quickly diagnose bacterial infection in the body.

How the Test is Performed

How the test is performed depends on what tissue or fluid from your body is being tested. The test may be quite simple, or you may need to prepare ahead of time.

• You may need to provide a sputum, urine, or stool sample.
• Your health care provider may use a needle to take fluid from your body to test. This could be from a joint, from the sac around your heart, or from the space around your lungs.
• Your provider may need to take a tissue sample, such as from your cervix or skin.

The sample is sent to a laboratory.

• A small amount is spread in a very thin layer on a glass slide. This is called a smear.
• A series of stains are added to the sample.
• A lab team member examines the stained smear under the microscope, looking for bacteria.
• The color, size, and shape of the cells help identify the specific type of bacteria.

How to Prepare for the Test

Your provider will tell you what to do to prepare for the test. For some types of tests, you will not need to do anything.

How the Test will Feel

How the test will feel depends on the method used to take a sample. You may not feel anything, or you may feel pressure and mild pain, such as during a biopsy. You may be given some form of pain medicine so you have little or no pain.

Why the Test is Performed

You may have this test to diagnose an infection caused by bacteria. It can also identify the type of bacteria causing the infection.

This test can help find the cause of various health problems, including:

• Intestinal infection or illness
• Sexually transmitted diseases (STDs)
• Unexplained swelling or joint pain
• Signs of a heart infection or fluid buildup in the thin sac that surrounds the heart (pericardium)
• Signs of infection of the space around the lungs (pleural space)
• Cough that will not go away, or if you are coughing up material with a foul odor or odd color
• Infected skin sore

A normal result means that no bacteria or only “friendly” bacteria were found. Some types of bacteria normally live in certain areas of the body, such as the intestines. Bacteria normally don’t live in other areas, such as the brain or spinal fluid.

Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may indicate an infection. You will need further tests, such as a culture, to find out more about the infection.

Risks

Your risks depend on the method used to remove tissue or fluid from your body. You may have no risk at all. Other risks are rare, but may include:

• Infection
• Bleeding
• Heart or lung puncture
• Collapsed lung
• Breathing problems
• Scarring

Routine sputum culture

Sputum culture

Routine sputum culture is a laboratory test that looks for germs that cause infection. Sputum is the material that comes up from air passages when you cough deeply

How the Test is Performed

A sputum sample is needed. You will be asked to cough deeply and spit any phlegm that comes up from your lungs into a special container. The sample is sent to a lab. There, it is placed in a special dish (culture). It is then watched to see if bacteria or other disease-causing germs grow.

How to Prepare for the Test

Drinking a lot of water and other fluids the night before the test may make it easier to cough up the sputum.

How the Test will Feel

You will need to cough. Sometimes the health care provider will tap on your chest to loosen deep sputum. Or, you may be asked to inhale a steamlike mist to help you cough up the sputum. You may have some discomfort from having to cough deeply.

Why the Test is Performed

The test helps identify the bacteria or other type of germs that are causing an infection in the lungs or airways (bronchi).

Normal Results

In a normal sputum sample, there will be no disease-causing germs.

What Abnormal Results Mean

If the sputum sample is abnormal, the results are called “positive.” Identifying the bacteria, fungus, or virus may help diagnose the cause of:

• Bronchitis (swelling and inflammation in the main passages that carry air to the lungs)
• Lung abscess (collection of pus in the lung)
• Pneumonia
• Tuberculosis
• Flare-up of chronic obstructive pulmonary disease (COPD) or cystic fibrosis

Risks

There are no risks with this test

Sputum direct fluorescent antibody (DFA) test

Direct immunofluorescence test; Direct fluorescent antibody – sputum

Sputum direct fluorescent antibody (DFA) is a lab test that looks for micro-organisms in lung secretions.

How the Test is Performed

You will produce a sputum sample from your lungs by coughing up mucus from deep inside your lungs. (Mucus is not the same as saliva or spit from the mouth.)

The sample is sent to a lab. There, a fluorescent dye is added to the sample. If the micro-organism is present, a bright glow (fluorescence) can be seen in the sputum sample using a special microscope.

How to Prepare for the Test

If coughing does not produce sputum, a breathing treatment may be given before the test to trigger sputum production.

How the Test will Feel

There is no discomfort with this test.

Why the Test is Performed

Your doctor may order this test if you have signs of certain lung infections.

Normal Results

Normally, there is no antigen-antibody reaction.

What Abnormal Results Mean

Abnormal results may be due to an infection such as:

• Legionnaire disease
• Pneumonia due to certain bacteria

Risks

There are no risks with this test.

Sputum fungal smear

KOH test; Fungal smear – sputum; Fungal wet prep; Wet prep – fungal

A sputum fungal smear is a laboratory test that looks for fungus in a sputum sample. Sputum is the material that comes up from air passages when you cough deeply.

How the Test is Performed

A sputum sample is needed. You will be asked to cough deeply and spit any material that comes up from your lungs into a special container.

The sample is sent to a lab and examined under a microscope.

How to Prepare for the Test

There is no special preparation.

How the Test will Feel

There is no discomfort.

Why the Test is Performed

Your health care provider may order this test if you have symptoms or signs of a lung infection, especially if you have a weakened immune system due to certain medicines or diseases such as cancer or HIV/AIDS.

Normal Results

A normal (negative) result means no fungus was seen in the test sample.

Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may be a sign of a fungal infection. Such infections include:

• Aspergillosis
• Blastomycosis
• Coccidioidomycosis
• Cryptococcosis
• Histoplasmosis

Risks

There are no risks associated with a sputum fungal smear.

Sputum stain for mycobacteria

Acid fast bacilli stain; AFB stain; Tuberculosis smear; TB smear

Sputum stain for mycobacteria is a test to check for a type of bacteria that cause tuberculosis and other infections.

How the Test is Performed

This test requires a sample of sputum.

• To do this, you will be asked to cough deeply and spit the substance that comes up from the lungs (sputum) into a container.
• You may be asked to breathe in a mist of salty steam. This makes you cough more deeply and produce sputum.
• If you still do not produce enough sputum, you might have a bronchoscopy .

The test sample is examined under a microscope. Another test, called a culture, is done to confirm the results. A culture test takes a few days to get results. This sputum test can give your doctor a quick answer.

How to Prepare for the Test

It can help to drink a lot of fluids the night before the test. It makes the test more accurate if it is done first thing in the morning.

How the Test Will Feel

There is no discomfort, unless a bronchoscopy needs to be performed.

Why the Test is Performed

The test is performed when the doctor suspects tuberculosis or other Mycobacterium infection.

Normal Results

Results are normal when no mycobacterial organisms are found.

What Abnormal Results Mean

Abnormal results show that the stain is positive for:

• Mycobacterium tuberculosis
• Mycobacterium avium-intracellular
• Other mycobacteria or acid-fast bacteria

Risks

There are no risks unless bronchoscopy is performed.

Considerations

To increase the accuracy of this test, it is sometimes done three times, often three days in a row.

More sophisticated tests are sometimes used to stain sputum for mycobacteria. Check with your health care provider to see if these are available in the laboratory.

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