• Also Known As:
  • ADA
  • Formal Name:
  • Adenosine Deaminase
  • fluid
Medically Reviewed by Expert Board.

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

This article was last modified on
Learn more about...

At a Glance

Why Get Tested?

To help detect or rule out a Mycobacterium tuberculosis infection in pleural fluid in order to assist in the diagnosis of tuberculosis; rarely to detect the infection in other body fluids such as peritoneal fluid or cerebrospinal fluid (CSF)

When To Get Tested?

When a health care practitioner suspects that someone with chest pain, coughing, and/or difficulty breathing has tuberculosis that has spread to their pleurae (lining around the lungs)

Sample Required?

A volume of pleural fluid is collected by a healthcare practitioner using a procedure called thoracentesis; other body fluids are collected using other procedures

Test Preparation Needed?


You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Adenosine deaminase (ADA) is a protein that is produced by cells throughout the body and is associated with the activation of lymphocytes, a type of white blood cell that plays a role in the immune response to infections. Conditions that trigger the immune system, such as an infection by Mycobacterium tuberculosis, the bacteria that causes tuberculosis (TB), may cause increased amounts of ADA to be produced in the areas where the bacteria are present. This test measures the amount of adenosine deaminase present in pleural fluid in order to help diagnose a tuberculosis infection of the pleurae.

Pleurae are membranes that cover the chest cavity and the outside of each lung. Small amounts of pleural fluid are continuously produced to lubricate the movement of the lungs against these membranes and the membranes against each other during inhalation and exhalation. A variety of conditions and diseases, including infection, can cause inflammation of the pleurae (pleurisy or pleuritis) and can lead to excessive pleural fluid accumulation (pleural effusion).

Tuberculosis can spread into the lungs and pleurae, causing symptoms such as chest pain, chronic cough, and shortness of breath. Since these symptoms may also be seen with a variety of other conditions, it is important to determine the cause as rapidly as possible in order to properly treat the affected person. Detecting mycobacteria in pleural fluid can be difficult because there may be a large volume of fluid and very low numbers of bacteria present. Though the ADA test is not specific and does not replace the culture for diagnosing TB, it may be positive even when numbers of bacteria are very low and can be used as an adjunct test to help determine whether tuberculosis is the likely source of a person’s symptoms.

How is the sample collected for testing?

A sample of pleural fluid is collected by a healthcare practitioner with a syringe and needle using a procedure called thoracentesis. Rarely, other body fluid samples, such as peritoneal or cerebrospinal fluid (CSF), are collected using procedures specific to the fluid type.


Common Questions

How is it used?

The adenosine deaminase (ADA) test is not a diagnostic test, but it may be used along with other tests such as pleural fluid analysis, acid-fast bacillus (AFB) smear and culture, and/or tuberculosis molecular testing to help determine whether a person has a Mycobacterium tuberculosis infection (tuberculosis or TB) of the lining of the lungs (pleurae).

A culture is considered the “gold standard” for diagnosing tuberculosis and guiding treatment, but it may take several days to weeks to complete. Molecular testing and the AFB smear are rapid tests, but they require that a sufficient number of microorganisms be present in the fluid to detect them. Pleural fluid presents a unique problem with detecting M. tuberculosis because there may be a large volume of fluid with a very low number of bacteria present. Though the ADA test is not definitive, it is a rapid test and may be elevated even when there are few bacteria present. ADA results may be used to help guide treatment until results from a culture are available.

The ADA test is used as an adjunct test to help rule in or rule out tuberculosis in pleural fluid. Rarely, it may be ordered to detect tuberculosis in other body fluids, such as peritoneal fluid or cerebrospinal fluid (CSF).

When is it ordered?

An ADA test may be ordered when a person has an accumulation of fluid in the chest cavity (pleural fluid) and has signs or symptoms that suggest TB, such as:

  • Chronic cough, sometimes with bloody sputum
  • Fever, chills
  • Night sweats
  • Unexplained weight loss
  • Chest pain

This test may be ordered as one of several tests to help rule in or rule out TB as the cause of a person’s symptoms, especially if the individual falls into a high-risk group, such as:

  • People with close contact with someone who has active infectious TB
  • Immigrants from areas of the world where the incidence of TB is high
  • Children younger than 5 years old who have a positive TB screening test
  • People who work with or are part of groups with high rates of infection, such as the homeless, IV drug users or confined populations, such as hospitalized patients, prisoners, and residents of nursing homes
  • People with weakened immune systems such as:
    • Those with HIV/AIDS
    • Those with chronic underlying conditions, including diabetes and kidney disease
    • Organ transplant recipients and others on immunosuppressant drugs
    • Pregnant women
    • The elderly

Testing may be ordered when a healthcare practitioner wants to determine whether a person likely has tuberculosis, in advance of other test results, in order to initiate treatment.

What does the test result mean?

If adenosine deaminase (ADA) is markedly elevated in pleural fluid in a person with signs and symptoms that suggest tuberculosis, then it is likely that the person tested has a M. tuberculosis infection in their pleurae. This is especially true when there is a high prevalence of tuberculosis in the geographic region where a person lives.

When there is a low prevalence of tuberculosis in a region, then a person may have tuberculosis or may have an ADA result that is elevated for another reason, such as cancer (particularly lymphomas), pulmonary embolus, sarcoidosis, or lupus. These other diagnoses are more likely if the ADA result is only mildly or moderately elevated.

A person with a low ADA level is unlikely to have tuberculosis in their pleurae. This does not rule out having the infection in other parts of their body.

If ADA is markedly elevated in fluid from another part of the body, such as peritoneal fluid or CSF, then there is an increased likelihood that tuberculosis is present in this area.

Is there anything else I should know?

The ADA test cannot positively identify M. tuberculosis as the cause of a person’s symptoms, and the test results cannot be used to determine if the person has drug-resistant tuberculosis.

Can my doctor diagnose tuberculosis without testing my pleural fluid?

A healthcare practitioner cannot diagnose tuberculosis in the pleural space without testing the pleural fluid. If the infection is present in your lungs, then sputum may be collected or, if meningitis is suspected, cerebrospinal fluid (CSF) would be tested.

Should everyone with suspected tuberculosis have an ADA test performed?

The ADA test is primarily performed when tuberculosis is suspected in the pleurae, and it is not routinely available in all laboratories. It will be performed when a healthcare practitioner determines that it will be useful and timely in helping to diagnose or rule out tuberculosis.

Can my blood be tested for ADA?

Yes, and it sometimes is, but it is done for another purpose and not to detect tuberculosis. The blood may be tested to help identify ADA deficiency.

What is ADA deficiency?

ADA is an enzyme that converts one byproduct into another byproduct. The first substance is toxic to lymphocytes and must be inactivated by ADA. With ADA deficiency, a rare inherited condition, the body makes insufficient ADA. This leads to the buildup of the toxic byproduct and can cause severe combined immunodeficiency disease (SCID). Infants with this condition have seriously compromised immune systems and may not survive without bone marrow transplantation. For more information, visit the Genetics Home Reference webpage on ADA deficiency.

View Sources

Sources Used in Current Review

Herchline, T. (Updated 2015 Oct 22). Tuberculosis. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/230802-overview. Accessed April 2016.

Hanson, K. (Updated 2016 Feb). Mycobacterium tuberculosis – TB. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/TB.html?client_ID=LTD. Accessed April 2016.

Arnold D, et al. Pleural Fluid Adenosine Deaminase (Pfada) in the Diagnosis of Tuberculous Effusions in a Low Incidence Population. PLoS One. 2015; 10(2): e0113047. Published online 2015 Feb 3. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315514/. Accessed April 2016.

Afrasiabian S, et al. Diagnostic value of serum adenosine deaminase level in pulmonary tuberculosis. J Res Med Sci. 2013 Mar; 18(3): 252–254. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732909/. Accessed April 2016.

Sources Used in Previous Reviews

Herchline, T. and Chavis, P. (Updated 2012 March 22). Tuberculosis. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/230802-overview. Accessed April 2012.

Chegou, N. et. al. (2011 May 27). Tuberculosis Assays: Past, Present and Future. Medscape Today News from Expert Rev Anti Infect Ther. 2011;9(4):457-469 [On-line information]. Available online at http://www.medscape.com/viewarticle/741840. Accessed April 2012.

Saleh, M. et. al. (2012 April). Use of adenosine deaminase measurements and QuantiFERON in the rapid diagnosis of tuberculous peritonitis. J Med Microbiol v 61(4) Abstract [On-line information]. Available online at http://jmm.sgmjournals.org/content/61/Pt_4/514.short?rss=1. Accessed April 2012.

Hanson, K. (Updated 2011 March). Mycobacterium tuberculosis – TB. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/TB.html?client_ID=LTD. Accessed April 2012.

Baba, K. et. al. (2008 July). Adenosine Deaminase Activity Is a Sensitive Marker for the Diagnosis of Tuberculous Pleuritis in Patients with Very Low CD4 Counts. PLoS ONE v 3(7): e2788 [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2464737/. Accessed April 2012.

Laniado-Laborín, R. (2005 Feberuary). Adenosine Deaminase in the Diagnosis of Tuberculous Pleural Effusion, Is It Really an Ideal Test? A Word of Caution. CHEST v 127 (2) 417-418 [On-line information]. Available online at http://chestjournal.chestpubs.org/content/127/2/417.full.html. Accessed April 2012.

Jiménez Castro, D. et. al. (2003 February 1). Diagnostic value of adenosine deaminase in nontuberculous lymphocytic pleural effusions. Eur Respir J 2003; 21: 220–224 [On-line information]. Available online at http://www.ersj.org.uk/content/21/2/220.full. Accessed April 2012.

Gupta, B. et. al. (2010 October). Adenosine Deaminase Levels in CSF of Tuberculous Meningitis Patients. J Clin Med Res. 2010 October; 2(5): 220–224. [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3104661/. Accessed April 2012.

(Reviewed 2008 February). Adenosine deaminase deficiency. Genetics Home Reference [On-line information]. Available online at http://ghr.nlm.nih.gov/condition/adenosine-deaminase-deficiency. Accessed April 2012.

Hershfield, M. (Updated 2011 December 22). Adenosine Deaminase Deficiency. GeneReviews [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/books/NBK1483/. Accessed April 2012.

(© 1995-2012). Test ID: FADA Adenosine Deaminase, Fluid. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/91554. Accessed April 2012.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 50-53.

Ask a Laboratory Scientist

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Send Us Your Question