What does AFB smear positive mean?

If your AFB smear was positive, it means you probably have TB or other infection, but an AFB culture is needed confirm the diagnosis. Culture results can take several weeks, so your provider may decide to treat your infection in the meantime.

What is AFB smear negative?

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.

How do you read an AFB smear?

A normal result for an acid-fast bacteria smear is negative, meaning no bacteria were found in the sputum sample. A positive result means that bacteria were found and that you may have an infection. The smear is treated with a special acid-fast stain that can provide a preliminary test result in 24 hours.

What is an AFB stain used for?

The acid-fast stain is a laboratory test that determines if a sample of tissue, blood, or other body substance is infected with the bacteria that causes tuberculosis (TB) and other illnesses.

Is smear-negative TB infectious?

Patients with sputum smear–negative TB are less infectious than patients with sputum smear–positive TB [1, 2]. Nevertheless, patients with smear-negative, culture-positive pulmonary TB are capable of transmitting M. tuberculosis [3, 4].

How is TB confirmed?

Test for TB Infection The Mantoux tuberculin skin test is performed by injecting a small amount of fluid called tuberculin into the skin in the lower part of the arm. The test is read within 48 to 72 hours by a trained health care worker, who looks for a reaction (induration) on the arm.

Is smear negative TB infectious?

What organisms are AFB positive?

[1] Bacteria displaying acid fastness include:

• Genus Mycobacterium – M. leprae, M. tuberculosis, M. smegmatis, M. Avium complex, M. kansasii.
• Genus Nocardia – N. brasiliensis, N. cyriacigeorgica, N. farcinica, and N. nova.

What is the difference between AFB smear and culture?

Positive AFB smears indicate a probable mycobacterial infection. However, a culture must be performed to confirm a diagnosis and identify the species of mycobacteria present.

What is smear test for TB?

Sputum smear microscopy, the primary method for diagnosis of pulmonary TB, is a simple, rapid, and inexpensive technique that is highly specific in areas with very high prevalence [8]. Its limitations include low sensitivity and diagnosis of extrapulmonary TB, pediatric TB, and patients coinfected with HIV [9].

What bacteria causes AFB?

Bacteria displaying acid fastness include:

• Genus Mycobacterium – M. leprae, M. tuberculosis, M. smegmatis, M. Avium complex, M. kansasii.
• Genus Nocardia – N. brasiliensis, N. cyriacigeorgica, N. farcinica, and N. nova.

How accurate is AFB smear?

RESULTS: Diagnostic accuracy of induced sputum AFB smear was found to be 92.85%, sensitivity 63.63%, specificity 97.26%, PPV 77.78% and NPV 95.67% (p-value <0.001)and that of BAL was found to be 86.90%, sensitivity 52.94%, specificity 95.52%, PPV 75% and NPV 88.89% (p-value <0.001).

What do the results of an AFB smear or culture mean?

What do the results mean? If your results on an AFB smear or culture were negative, you probably don’t have active TB. But it could also mean there weren’t enough bacteria in the sample for your health care provider to make a diagnosis.

How long does it take for AFB smears to be reported?

AFB smears are reported within 24 hours of receipt; AFB cultures are reported: (1) at 6 weeks when no growth occurs or (2) when growth occurs and identification is made.

What is an acid-fast Bacilli (AFB) smear?

Acid- Fast Bacilli (AFB) smear and culture are two separate tests always performed together at the MSPHL, Tuberculosis (TB) Unit.

How do you get a sputum sample for an AFB smear?

Your health care provider will need a sample of your sputum for both an AFB smear and an AFB culture. The two tests are usually done at the same time. To get sputum samples: 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.