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Why Get Tested?
To help detect and identify infections caused by Mycobacterium tuberculosis, the cause of tuberculosis (TB), and other Mycobacterium species, which are known as acid-fast bacilli (AFB); to monitor the effectiveness of treatment
When To Get Tested?
When you have signs and symptoms of a lung infection, such as a chronic cough, weight loss, fever, chills, and weakness, that may be due to TB or a nontuberculous mycobacterial (NTM) infection; when you have a positive TB screening test and you are in a high-risk group for progressing to active disease; when you have a skin or other body site infection that may be due to mycobacteria; when you are undergoing treatment for TB
Sample Type:
Sputum,Any Specimen/Slides
Fasting :
NO
Report Delivery:
3rd Day
Components:
1 Observations

Tests Detail

Observations Included

Sputum For AFB Stain

Ziehl - Neelsen Stain

The Test marked with (*) are in our NABL Scope.

Sample Report

Test Name	Modified AFB (ZN) Stain
Report Availability	3rd Day
Code	M4033
Category	SA-Special Advance
Schedule	Daily
TAT*	48
Tested At*	SHRS
Method	Microscopy
Brief Description	Presumptive diagnosis of Tuberculosis

*Reporting TAT in days
for the samples recieved by 4PM

*0 = Same Day, 1 = Next Day, 2 = 2nd Day,
3 = 3rd Day So on from Schedule

*NPL : Tested @ Sarvodaya Diagnostics
NRL : Tested @ NPL Outsource lab

Also Known As:
AFB Smear and Culture TB Culture and Sensitivity Mycobacteria Smear Mycobacteria Culture TB NAAT Aci
Formal Name:
Basic Metabolic Panel
Sample Instructions:
For suspected cases of tuberculosis lung infections, usually three sputum samples are collected early in the morning on different days. If the affected person is unable to produce sputum, a bronchoscope may be used to collect fluid during a procedure called a bronchoscopy. In children, gastric washings/aspirates may be collected. Depending on symptoms, urine, an aspirate from the site of suspected infection, cerebrospinal fluid (CSF), other body fluids, or biopsied tissue samples may be submitted for AFB smear and culture.
Test Preparation Needed?
None
What Is Being Tested?
Most samples that are submitted for acid-fast bacilli (AFB) testing are collected because the health practitioner suspects that a person has tuberculosis (TB), a lung infection caused by Mycobacterium tuberculosis. Mycobacteria are called acid-fast bacilli because they are a group of rod-shaped bacteria (bacilli) that can be seen under the microscope following a staining procedure where the bacteria retain the color of the stain after an acid wash (acid-fast). AFB laboratory tests detect the bacteria in a person's sample and help identify an infection caused by AFB. There are a several types of AFB that may be detected with this testing; however, the most common and medically important ones are members of the genus Mycobacterium. Mycobacterium tuberculosis is one of the most prevalent and infectious species of mycobacteria. Since TB is transmitted through the air when an infected person sneezes, coughs, speaks, or sings, it is a public health risk. It can spread in confined populations, such as in the home and schools, correctional facilities, and nursing homes. Those who are very young, elderly, or have preexisting diseases and conditions, such as AIDS, that compromise their immune systems tend to be especially vulnerable. AFB testing can help track and minimize the spread of TB in these populations and help determine the effectiveness of treatment. Another group of mycobacteria referred to as nontuberculous mycobacteria (NTM) can also cause infections. However, only a few of the more than 60 species of mycobacteria that have been identified cause infections in humans. Some examples include Mycobacterium avium-intracellulare complex (MAC), which can cause a lung infection in people with weakened immune systems, and Mycobacterium marinum, which can cause skin infections. (See the article on Nontuberculous Mycobacteria for more details on different types). In addition to TB, AFB testing can help identify infections caused by these nontuberculous mycobacteria. AFB
How Is It Used?
AFB testing may be used to detect several different types of acid-fast bacilli, but it is most commonly used to identify an active tuberculosis (TB) infection caused by the most medically important AFB, Mycobacterium tuberculosis. Mycobacteria are called acid-fast bacilli because they are rod-shaped bacteria (bacilli) that can be seen under the microscope following a staining procedure in which the bacteria retain the color of the stain after an acid wash (acid-fast). A few different tests may be used to help identify AFB as the cause of an infection: An AFB smear is used as a rapid test to detect mycobacteria that may be causing an infection such as tuberculosis. The sample is spread thinly onto a glass slide, treated with a special stain, and examined under a microscope for "acid-fast" bacteria. This is a relatively quick way to determine if an infection may be due to one of the mycobacteria, such as M. tuberculosis. AFB smears can provide presumptive results within a few hours and are valuable in helping to make decisions about treatment while culture results are pending. However, this rapid test is less sensitive than culture to diagnosis a mycobacterial infection. A molecular test for TB called nucleic acid amplification test (NAAT) may be done in conjunction with an AFB smear. NAAT detects the genetic components of mycobacteria by amplifying/replicating pieces of the microorganisms' genetic material. These tests can help decrease the amount of time necessary for a presumptive diagnosis of tuberculosis to less than 24 hours. The testing can narrow the identification to a complex of mycobacteria (a combination, of which M. tuberculosis is the most common). They are fairly sensitive and specific when they are performed on specimens where acid-fast bacteria were seen on the smear. When they are done on samples that are AFB-negative by smear, they tend to be less sensitive. The test methods are approved for respiratory samples but must be confirmed with
When Is It Ordered
AFB testing is ordered when: Someone has symptoms that suggest pulmonary TB or other mycobacterial lung infection, such as: Lingering, chronic cough that produces phlegm or sputum, sometimes with bloody streaks Fever, chills Night sweats Loss of appetite Unexplained weight loss Weakness, fatigue Chest pain A person has symptoms associated with a TB or other mycobacterial infection located outside of the lungs (extrapulmonary); the symptoms vary depending on the area of the body that is affected. Some examples include back pain and paralysis (spinal TB), weakness due to anemia (TB in the bone marrow), altered mental state, headache, and coma (TB meningitis), joint pain or abdominal pain. A TB screening test is positive and the person is at increased risk for active disease and/or characteristic signs are seen in an X-ray of the lung. Someone has been in close contact with a person who has been diagnosed with TB and the exposed person either has symptoms or has a condition or disease that puts him or her at a much higher risk of contracting the disease, such as HIV/AIDS. (Those with AIDS are more likely than other affected people to have extrapulmonary TB with a few, vague symptoms.) An individual is being treated for TB; AFB testing is usually ordered at intervals, both for evaluating the effectiveness of treatment and for determining whether or not a person is still infectious. An individual has a chronic skin infection that does not respond to the usual antibiotics given for a bacterial infection; NTM may be the cause of the infection since they do not respond to the same antibiotics used to treat a staphylococcal or streptococcal infection.
What Does The Test Result Mean?
AFB Smear and NAAT A negative AFB smear may mean that no infection is present, that symptoms are caused by something other than mycobacteria, or that the mycobacteria were not present in sufficient numbers to be seen under the microscope. Usually three samples are collected to increase the probability that the organisms will be detected. Nevertheless, if AFB smears are negative and there is still a strong suspicion of a mycobacterial infection, then additional samples may be collected and tested on different days. A smear negative sample may still grow mycobacteria since the culture media allows low numbers of bacteria that cannot be seen in a microscopic examination to multiply and be detected. 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. For people with signs and symptoms of an active TB infection, AFB smear results are considered together with results from NAAT for TB, as recommended by the Centers for Disease Control and Prevention. Though definitive diagnosis requires results from a culture, results from the smear and NAAT may be helpful in deciding what to do. For example, if there is a presumptive diagnosis of TB based on rapid test results, most health practitioners would treat. Interpretation of smear and NAAT results are summarized in the following table. Again, all results must be confirmed by results from culture. AFB smear result NAAT result for TB Interpretation Positive Positive Presumptive diagnosis for TB Negative Positive NAAT is more sensitive than smear so this may occur in people with true disease; may test additional samples using NAAT. If more than one sample is positive by NAAT, this is a presumptive diagnosis for TB. Positive Negative Questionable results for TB; an inhibitor may be present in the specimen or the AFB seen on the smear are not M. tuberculosis. A test for the inhibitor may be performed.
Is There Anything Else I Should Known?
TB requires a lengthy course of multiple antibiotics to eradicate an active infection. People with inactive (latent) infections, although asymptomatic, may be treated with a single drug to reduce the risk of having an active infection in the future. A faster lab method to culture Mycobacterium tuberculosis has been developed. Culturing the sample in a liquid broth-based medium allows the organisms to be detected sooner. Some of the broth cultures require an automated instrument to detect the presence of the mycobacteria, while other methods can be read manually. A liquid culture method, called Microscopic-Observation Drug-Susceptibility (MODS) assay, takes only about 7 days to diagnose TB and detects bacterial resistance to antibiotics at the same time. Since this method can recognize the presence of multidrug-resistant TB (MDR-TB) much more quickly than conventional culture, it can help health practitioners diagnose and treat the disease at an earlier stage and has the potential to help control the spread of infectious TB. The benefits and limitations of this non-automated test are still being evaluated in resource-limited countries with high prevalence of TB. In December 2010, the World Health Organization recommended use of a fully automated, cartridge-based nucleic amplification assay that can simultaneously detect TB and rifampicin resistance directly from sputum in less than two hours. It was approved for marketing in the U.S. in July 2013 and this technology has been recently adopted by many laboratories. However, this NAAT test does not replace AFB cultures. All samples submitted for AFB testing should be cultured to ensure that any mycobacteria that are present are available for further testing, according to the Centers for Disease Control and Prevention. Can I have a tuberculosis (TB) infection and not be sick? Yes. There are many people in the United States and worldwide who have a latent form of TB infection. They have been exposed to the bacteria, bu

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