Adenosine Deaminase

Also Known As

ADA

Formal Name

Adenosine Deaminase, Fluid

This article was last reviewed on

28 December 2012.

This article waslast modified on 6 December 2017.

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 doctor suspects that someone with chest pain, coughing, and/or difficulty breathing has tuberculosis that has spread from their lungs to the pleurae (lining around the lungs)

Sample Required?

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

Test Preparation Needed?

None required

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read 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 occurs most commonly in the lungs, and it can spread into the 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. The ADA test is not as accurate as a culture for diagnosing TB, however results will be available much quicker so it can be used as an additional 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 doctor with a syringe and needle using a procedure called thoracentesis. Rarely, other body fluid samples, such as peritoneal or CSF, are collected using procedures specific to the fluid type.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

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). It may also be used to aid the diagnosis of TB meningitis.

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 initially until results from a culture are available.

The ADA test is used as an additional test to help rule in or rule out tuberculosis in pleural fluid. Rarely, it may be requested to detect tuberculosis in other body fluids, such as peritoneal fluid or cerebrospinal fluid (CSF).
When is it requested?
An ADA test may be requested when a person has an accumulation of pleural fluid and symptoms that suggest a M. tuberculosis infection. Signs and symptoms of tuberculosis (TB) affecting the lungs may include:

Chronic cough, sometimes with bloody sputum

Fever, chills

Night sweats

Unexplained weight loss

Weakness

Chest pain

This test may be requested 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 hospitalised 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 requested when a doctor 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 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 systemic lupus erythematosus (SLE). These other diagnoses are more likely if the ADA result is only mildly or moderately elevated.

A person with a low ADA result 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?

The doctor 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, 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 doctor 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, which is a very rare inherited disorder causing severe immunodeficiency in children.
What is ADA deficiency?

ADA is an enzyme that converts one by-product 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 build up of the toxic by-product 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.

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