Sputum for AFB (Acid-Fast Bacillus)

Sputum for AFB (Acid-Fast Bacillus), The sputum for AFB (Acid-Fast Bacillus) test is a diagnostic procedure used to detect the presence of mycobacteria, particularly Mycobacterium tuberculosis, the causative agent of tuberculosis (TB). In this test, a sample of sputum (mucus from the lower airways) is collected from the patient and stained using a special dye.

Under a microscope, acid-fast bacilli retain the dye and appear as bright red rods against a blue background, indicating a positive result. This test is crucial for the early diagnosis and treatment of tuberculosis, helping to control the spread of the disease.

Sputum Stain for Mycobacteria

Sputum stain for Mycobacteria is a laboratory test performed on a sample of your sputum, or phlegm. It’s also known as an acid-fast bacillus (AFB) stain or a tuberculosis (TB) smear.

Why the test is ordered

Your doctor will order this test if they think you have a mycobacterial infection.

Mycobacteria are a type of microorganism with nearly 100 known species. The most common type is Mycobacterium tuberculosis, which causes TB. The general symptoms of TB include:

• coughing up blood or mucus
• a lack of appetite
• weight loss
• weakness
• fatigue
• a fever
• chills
• night sweats

Another fairly common type of this bacteria is Mycobacterium leprae, which causes leprosy, also known as Hansen’s disease. The symptoms of Hansen’s disease include:

• skin discoloration
• skin lesions
• skin nodules
• skin plaques
• thickened skin
• nasal congestion
• nosebleeds

Except for the two microorganisms that cause TB and Hansen’s disease, most Mycobacteria exist in the water and soil everywhere in the world. These are called nontuberculous mycobacteria (NTM).

NTM live in:

• City water
• bayous
• rivers
• hot tubs
• swimming pools
• yard soil
• food

How to collect a sample of your sputum

To collect a sputum sample, you should do the following:

1. Brush your teeth and rinse your mouth without using antiseptic mouthwash.
2. Take a couple of long, deep breaths.
3. Breathe deeply again and cough hard until sputum comes up.
4. Spit out the sputum into the sample cup.
5. Keep coughing up sputum until the cup is filled to the marker, which is approximately 1 teaspoon.
6. Screw on the cup lid, and wash and dry the outside of it.
7. Write your name, your date of birth, and the date of collection on the cup label.

Take the sample to the clinic or laboratory, as instructed. The sample can be refrigerated for up to 24 hours if needed. Don’t freeze it or store it at room temperature.

If you can’t cough up sputum, try breathing the steam from boiling water or take a hot, steamy shower. The sputum must come from deep inside your lungs for the test to be accurate.

If you still cannot cough up sputum, your doctor will do a bronchoscopy to collect sputum directly from your lungs.

Methodology:

• AFB smear – fluorochrome staining
• AFB culture – B-D MGIT system and conventional culture media.

Specimen Collection

Specimen Source(s):

• UCD Health Systems
• Hospital Based Clinics / HBC
• Physician Clinics Network / PCN
• Others

Materials:

• Parafilm
• Sterile containers
• Small and large plastic biohazard bags
• Biohazard stickers

Acceptable Specimen Type(s):

• Sputum
• Bronchial Washing
• Pleural Fluid

Sputum:

• Specimen/Sputum collection best practice for initial diagnosis of tuberculosis:
  – Early morning, deep cough specimen, three (3) consecutive days collection.
  – A minimum of eight (8) hours must be allocated between specimens if sputum is collected within the same 24-hour period,
  – Minimum acceptable specimen volume: two (2) mL
  – Refrigerate until transported

Bronchial Washing:

• Preferred minimum acceptable volume: two (2) mL
• Refrigerate until transported

Pleural Fluid:

• Preferred minimum volume: two (2) mL
• Refrigerate until transported

Unacceptable Conditions:

1. Specimens that are not labeled with the patient name or identifier.
2. Clinical specimen collected within eight hours of the previous specimen.
3. Clinical specimens received greater than three (3) days from collection.
4. Specimen leaking on arrival.
5. Insufficient specimen volume (less than 2 mL).
6. Interfering Substances

Result Report Timing

1. AFB smears are reported within 24 hours of receipt
2. AFB cultures are reported:
   (a) when growth occurs and identification is made
   or
   (b) In the 7th week when no growth occurs

Possible Results:

AFB Smear:

Number of AFB observed at 100x magnification:
1+ (Rare) = 1-9 / 100 fields
2+ (Few) = 1-9 / 10 fields
3+ (Moderate) = 1-9 / field
4+ (Many) = greater than 1-9 / field
AFB Not Found
Smear Not Performed

Patient instructions:

Collection of Sputum/Phlegm/Saliva Sample

Please carefully follow the steps below.

1. Gargle with water immediately before obtaining a sputum specimen to reduce the number of oral bacteria. Do not use a mouthwash or any other gargle.
2. Open the lid of the container.
3. Try coughing as strongly as you can while holding the tissue over your nose and mouth.
4. When you are ready to spit, do it into the cup/vial, spitting any phlegm with saliva. If you are not able to produce any phlegm while coughing, spit saliva into the cup/vial.
5. Press the rim of the specimen container under the lower lip to catch all the expectorated or coughed sputum.
6. Cough deeply and expectorate sputum (not saliva) into the cup.
7. Close the lid securely and notify your caregiver that your specimen is ready for transport to the laboratory.

NOTE: To have enough samples, it is permitted to spit multiple times into the container. Spitting 2-3 times into the container should provide enough material for testing.

When Your Doctor May Order an AFB Stain

There are a few reasons that you may need this test, including:

You have a lung infection. If you have symptoms of a lung infection, your doctor may use an AFB stain to explore the cause. These symptoms often include a chronic or long-lasting cough, coughing up blood, significant weight loss, fever, chills, and fatigue.

You’re high-risk or positive for TB. If a skin or blood test comes back positive for tuberculosis, or if you have a weakened immune system due to a condition like human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS), your doctor may use this test to further see if the disease is present. You might also be considered high-risk if you have been in a hospital, nursing home, or correctional facility.

You have TB outside of your lungs. While tuberculosis often impacts your lungs, it can also infect other parts of your body like your spinal cord or kidneys. Your doctor may use an AFB stain to see if it is affecting your lungs as well as other places.You have HIV or AIDS. If you have HIV, AIDS, or a similar condition, you are more at risk for contracting TB. If you’ve been exposed to someone positive for tuberculosis, this test can help tell if you have contracted it.

You’ve had a TB infection. Finally, your doctor may use this test if you have been successfully cured of TB. An AFB stain can help confirm that your recovery is complete and the tuberculosis is gone.

What Do the Results Mean?

If your AFB stain does not have any bacteria that hold onto the dye, then the result is considered negative. This means that you most likely do not have TB or another mycobacterial infection in your lungs.

If there is a small number of bacteria that keep their dye color, the results may be considered an early positive or inconclusive. The more bacteria that are seen under the microscope, the more intensely positive and infectious you probably are. A positive test will inform your doctor as to what is causing your infection, and what the next treatment steps might be. If you have TB, you will be treated with anti-tuberculosis medication.

False-positive and false-negative results are possible. If your results are inconclusive, or your doctor thinks that the test may not be accurate, your provider may order other scans or testing to get more information on your condition.

What happens during AFB testing?

• You will be asked to cough deeply and spit into a sterile container. You will need to do this for two or three days in a row. This helps make sure your sample has enough bacteria for testing.
• If you have trouble coughing up enough sputum, your provider may ask you to breathe in a sterile saline (salt) mist that can help you cough more deeply.
• If you still can’t cough up enough sputum, your provider may perform a procedure called a bronchoscopy. In this procedure, you will first get medicine so you won’t feel any pain. Then, a thin, lighted tube will be put through your mouth or nose and into your airways. The sample may be collected by suction or with a small brush.