Required section · Section 2 of 6
Why CSF is normally almost empty
Cerebrospinal fluid (CSF) is formed mainly by the choroid plexus and circulates through the ventricles, cisterns, and subarachnoid space before it is reabsorbed. The blood-brain barrier restricts the movement of macromolecules and cells from blood into this compartment, which is the physiologic reason normal CSF carries very little protein and very few nucleated cells compared to blood or most other body fluids.
That low baseline is exactly what makes CSF cell counting demanding. A manual count that is easy to perform on a cloudy synovial fluid with thousands of cells per microliter has almost nothing to count in a normal CSF specimen, so a small technical error, a stray contaminant, or a few minutes of cell degeneration can move the result by a clinically meaningful fraction.
Because there is so little cellular material to begin with, the laboratory leans on process discipline rather than on the count itself to keep the result trustworthy: correct tube handling, prompt mixing and examination, a chamber suited to low cellularity, and a duplicate count that is checked for agreement before anything is released.
A CSF cell count is only as good as the specimen handling that preceded it, because the biology gives the laboratory very little room for technical error.
From collection to a released CSF cell count
Collect and label
Tubes are drawn in sequence, labeled with source, tube number, and collection time. A short-filled tube is documented, not silently topped off.
Receive and triage
Received time is logged. The laboratory records available volume per tube and applies the local multidisciplinary allocation policy rather than assuming tube number sets the order.
Allocate by priority
Chemistry, microbiology, and the cell-count bench each receive the tube and volume the local policy assigns, coordinated across disciplines rather than fixed by tube number alone.
Mix and examine immediately
The cell-count tube is gently inverted to resuspend settled cells, then charged and examined without delay, because cell lysis and degeneration begin changing the picture from the moment of collection.
Count and calculate
Both chamber sides are counted per local procedure, checked for agreement, and the validated chamber-specific formula is applied to reach a reportable concentration.
Report with context
The laboratory releases the observed result together with tube identity, timing, and any specimen limitation, and does not substitute a calculated correction for an observed result.
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