Adenosine Deaminase Test

ADA is a common biomarker for pulmonary and extrapulmonary tuberculosis. An ADA test proves to be an important diagnostic tool in conditions such as pneumonia, meningitis and some malignancies where the infection is due to the tubercular pathogen, manifesting in the form of high ADA levels in effusion fluids.

Tubercular infection of the peritoneum also shows a high concentration of ADA in ascitic fluid. ADA test is recommended as an ancillary test to the main diagnostic tests of tuberculosis and some other conditions. This test is done in case the following symptoms are seen

• Cough and cold
• Chest pain
• Pleural effusion
• Tuberculosis
• Pneumonia
• Ascites
• Synovitis
• Haemolytic anaemia 
• Meningitis

ADA test is not only a supportive diagnostic tool for tubercular infections but also used as a treatment response index.

ADA test is a simple analytical test that does not require fasting. A suitable technique is used to aspirate or drain the effusion fluid from a site in body. The patient is well informed about the aspiration or draining technique to be used before sample collection. For hospitalised patients, it is a simple bedside procedure.

For pleural effusion, a chest drain procedure is carried out by experienced doctors under extremely sterile conditions. Sometimes, fluid is aspirated through thoracentesis, in which, a system is temporarily inserted into the pleural space of the patient, and air and fluid are aspirated.

For ascitic effusion, paracentesis is performed for aspirating the fluid. 

Similarly, fluid can be aspirated from the synovial cavity, and CSF can also be collected. The site of drain tube insertion is cleaned with an antiseptic, and aseptic techniques are used to collect the sample. Patients might experience minor pain at the site of tube insertion, but the overall procedure is safe and simple.

For collecting serum sample, blood is withdrawn from a vein in the patient's arm and is collected in a sterile container to be sent to a lab for testing.

Normal results: ADA concentrations are measured in the serum, pleural effusions, synovial fluid, peritoneal fluid and CSF. Several studies carried out to determine normal and abnormal ADA levels suggest that concentration of 40 units (U)/litre (L) is the cut-off value for tubercular infections. A concentration of less than 40 IU/L indicates the absence of tubercular infection. For CSF, a level of up to 10 IU/L suggests the absence of tubercular infection in brain.

Abnormal results: ADA values above 40 IU/L are considered abnormal. High concentrations are commonly seen in pleural, synovial, ascitic effusions and serum of tuberculosis patients. Abnormal values suggest the presence of the following conditions:

• Tuberculosis with pleural effusion
• Synovitis commonly associated with rheumatoid arthritis
• Tubercular ascites
• Tubercular lymphadenitis
• Tubercular meningitis
• Tuberculous pneumonia

Tuberculosis is the most common infection in India. Pulmonary and extrapulmonary tuberculosis are associated with high concentrations of ADA enzyme. ADA test provides a useful, sensitive and specific tool for diagnosing tubercular infections. This test can also be used as a treatment response index for better management of tuberculosis.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational perspective and is in no way a substitute for medical advice from a qualified doctor.