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Haematology
TLC Fluid measures the total number of white blood cells in a sample of body fluid, such as fluid from around the spinal cord, a joint, or the chest or abdominal cavity, rather than in your blood. Unlike blood, which normally carries thousands of white cells in every microlitre, most of these fluids have very few white cells when everything is normal, so even a modest rise can be meaningful. Cerebrospinal fluid is a good example: a normal sample has only a handful of white cells, and a distinctly higher count is one of the first signs a doctor looks for when trying to work out whether meningitis or another central nervous system problem is present.
The report gives a total white cell count for the specific fluid tested, generally per microlitre, and it's almost always read alongside a differential showing what share of those cells are polymorphs versus lymphocytes. For cerebrospinal fluid specifically, MedlinePlus lists a normal range of 0 to 5 white blood cells, all of a single, mononuclear type; a count meaningfully above that range points toward infection, inflammation, or bleeding into the fluid. The same low-baseline logic applies to other body fluid TLC results, though normal baselines differ by fluid type.
Most fluid-filled spaces in the body, whether around the spinal cord, inside a joint, or lining the chest and abdominal cavities, normally contain very few white blood cells, because there's no ongoing immune activity there when everything is healthy. TLC Fluid takes advantage of that low baseline: because the starting point is so close to zero, even a moderate rise in white cells is a clear signal that something is happening in that space.
Blood always carries a substantial white cell population as a matter of course, so its total count moves within a wide expected range. Body fluids like cerebrospinal fluid don't, which is why a cerebrospinal fluid count of even a few dozen white cells, well within what would be an unremarkable blood result, can be a meaningful finding in that context.
In cerebrospinal fluid, a raised TLC is one of the first values a doctor checks when investigating suspected meningitis or another infection or inflammatory condition affecting the brain and spinal cord, and it's read together with the cell type breakdown, protein, and glucose levels rather than alone. In joint or other body cavity fluid, a raised TLC similarly signals that something, infection, inflammation, or bleeding, is affecting that space, and the same fluid sample is typically examined further for its cell-type mix and other findings to narrow down the cause.
TLC measures white blood cells in your blood, where a fairly high count is normal. TLC Fluid measures white cells in a body fluid like cerebrospinal or joint fluid, where the normal count is very low, so even a modest rise is meaningful.
MedlinePlus lists a normal range of 0 to 5 white blood cells in cerebrospinal fluid. Ranges can vary slightly by lab, so check the range printed on your own report.
It suggests infection, inflammation, or bleeding affecting the brain or spinal cord, such as meningitis. Your doctor reads it together with the cell-type breakdown and other cerebrospinal fluid values before drawing conclusions.
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.
It's commonly done on cerebrospinal fluid, joint fluid, and fluid collected from the chest or abdominal cavity. Other body fluids obtained during a diagnostic procedure can be tested the same way.
Not on its own. It's usually reported alongside a cell-type differential, and often protein, glucose, and culture results from the same sample, since the combination narrows down the cause more than the count alone.
It depends on which fluid is being tested; cerebrospinal fluid is collected by lumbar puncture, while joint fluid is collected by a needle draw from the joint. Ask your doctor about the specific procedure for your situation.