Finding the right tests…
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Finding the right tests…
Biochemistry
This is a general order for adenosine deaminase testing on a body fluid drawn by needle from a space other than the abdomen, most often fluid around a lung or around the heart, when tuberculosis is suspected there. It measures the same enzyme as the ascitic fluid, CSF, and blood versions of this test, but is used specifically when the fluid in question is neither cerebrospinal nor ascitic (abdominal) fluid, since a dedicated, separate test exists for each of those. Pleural fluid ADA is the best studied of this group, correctly identifying tuberculosis in roughly 9 in 10 people who have it, with a broadly similar result for pericardial fluid, though the exact cutoff differs by fluid type.
The lab reports ADA activity, in units per litre, from whichever fluid was sent, commonly pleural fluid drawn by a chest tap or pericardial fluid drawn from around the heart. Each fluid type has its own studied cutoff: around 40 U/L for pleural fluid, where it correctly identifies about 89 to 92 in every 100 people with tuberculous pleurisy, and a similar 40 U/L figure for pericardial fluid, correctly identifying about 88 in every 100 people with tuberculous pericarditis. The same fluid sample is usually tested for cell counts, protein, and glucose alongside ADA.
Fluid that collects around the lungs or the heart when tuberculosis is present is generally packed with the same immune cells that respond to the infection everywhere else in the body, so ADA measured directly in that fluid tends to run far higher, and far more reliably, than the same enzyme measured in blood. That's the basic reason fluid-based ADA testing exists as its own category rather than relying on a blood sample alone.
Pleural fluid ADA is the most extensively studied version of this test, generally read against a cutoff around 40 U/L, with published research putting sensitivity for tuberculous pleurisy at roughly 89 to 92 percent and specificity around 90 to 93 percent. Pericardial fluid ADA, tested the same way for suspected tuberculous pericarditis, performs similarly at the same 40 U/L cutoff, with sensitivity around 88 percent and specificity around 83 percent in published data. Because the immune response and the background causes of fluid buildup differ by location, each fluid type keeps its own studied threshold rather than sharing one blanket number.
A single ADA result, however high, is read together with the fluid's other findings, cell counts, protein, and glucose, and with imaging and clinical history, rather than treated as a stand-alone diagnosis. This is one reason the fluid sample is usually collected and sent for several tests at once, not ADA alone.
Ascitic fluid ADA is a dedicated, separately ordered test for fluid in the abdomen. This test covers other fluid types, most often pleural or pericardial fluid, each with its own studied cutoff.
Research generally uses a cutoff around 40 U/L, at which the test correctly identifies roughly 89 to 92 in every 100 people with tuberculous pleurisy.
It performs similarly at the same 40 U/L cutoff, with sensitivity around 88 percent, though it's somewhat less specific than pleural fluid ADA in published studies.
It's collected by a needle aspiration from the relevant space, such as a chest tap for pleural fluid or a pericardial tap for fluid around the heart, usually performed by a doctor with imaging guidance.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Yes, to a lesser extent — which is why the result is read together with the fluid's other findings and the clinical picture rather than assumed to confirm tuberculosis by itself.
Because the background rate of immune cells and other causes of fluid buildup differ by location in the body, each fluid type has been studied and calibrated separately for the most accurate cutoff.