What is an Adenosine Deaminase Test?

ADA activity higher than 43U/ml in the pleural fluids generally indicates pleural tuberculosis with 81- 100% sensitivity and above 83% specificity.

Higher ADA values also may be caused by health conditions, such as pulmonary embolism, lupus, lymphomas, sarcoidosis, and other parapneumonic and vascular diseases. However, in these cases, the ADA values are slightly higher.

Adenosine Deaminase testing is typically conducted to identify tuberculosis (TB) patients, but it can also be used to detect infections in the cerebrospinal and peritoneal fluids.

The test is also conducted to screen certain groups of people, such as: 

• Health workers working with tuberculosis patients
• People moving from tuberculosis-prone areas
• Pregnant women
• Children with a positive TB screening test result
• Immuno-deficient patients

The ADA test involves collecting pleural fluid from the pleural cavity of the chest. This procedure involves inserting a needle between the pleural membranes surrounding the chest and lungs and draining the aspirate through the tube. This fluid is then sent to the lab for immunoassay.

Side effects may include pain at the injection site, fever, breathing difficulties, and chest pain.

Multiple studies have suggested the ADA test for early diagnosis of tuberculosis in conjunction with the AFB smear test to detect the presence of acid-fast bacteria in a patient’s bodily samples.

Generally, serum ADA levels are considered 92.7% sensitive and 88.1% specific in pulmonary TB patients. However, you must compare the levels with other tests to distinguish between TB and other pulmonary infections.

The normal range of the Adenosine Deaminase test in males and females regardless of age is 40 units/L. Test results showing higher values are considered abnormal and indicates:

• Pleural tuberculosis
• Synovitis caused by rheumatoid arthritis
• Pneumonia associated with tuberculosis
• Tubercular ascites
• Meningitis of tuberculosis
• Lymphadenitis of tuberculosis

There are no set rules for preparing for an ADA test. Fasting is not required before the test. However, if you are on any medication, you must inform your physician since certain chemicals, such as blood thinners, may interfere with the test. 

If you are undergoing the test, it is advisable to bring someone to accompany you home, as you might feel dizzy due to the anaesthetic used during the test.

The sample for the ADA test is the pleural fluid collected by a registered medical professional by a procedure called thoracentesis. While the patient is seated with their ribs fully spread, the physician inserts a sterile needle to apply local anaesthesia. The aspirate is then drained into a tube aseptically, guided by an X-ray machine inside the pleural cavity. The procedure takes a minimum of 15 minutes.

ADA deficiency symptoms are as follows:

• Frequent diarrhoea
• Sweating at night
• Pneumonia
• Frequent fevers
• Chills
• Unprecedented weight loss
• Constant chest pain
• Excessive skin allergies and rashes
• Chronic cough

ADA-deficient children generally lag in their motor development compared to normal children.

ADA deficiency is generally detected through WBC counts and the analysis of vious immunoglobulin levels in T-cells, B-cells, and other natural killer cells of the immune system.

Biochemical genetic tests can establish a diagnosis of ADA deficiency. Biochemical analysis shows decreased ADA activity of less than 1% and increased levels of other dATP metabolites such as dAMP, dADP, and dATP in the erythrocytes.

Genetic analysis of probable mutations in the ADA genes confirms the disease.