Required section · Section 2 of 6
What a cytospin is built to show
Normal lumbar CSF has very few cells. This case laboratory's validated adult TNC interval is 0 to 5 nucleated cells per microliter, and the cells present are predominantly mononuclear, meaning lymphocytes and monocytes rather than neutrophils. Because the true cell count is so low, spreading a drop of CSF directly onto a slide the way you would a peripheral blood smear does not give you enough cells to identify reliably.
A cytocentrifuge (cytospin) solves that concentration problem. It spins a measured volume of specimen so the cells sediment onto a small area of the slide while the fluid is absorbed away, producing a monolayer dense enough for a manual differential and morphology review. The cytospin is a concentration and morphology preparation, not the cell count itself. The total nucleated-cell and RBC counts are performed and validated separately, on a hemocytometer or equivalent method, and the cytospin differential is reported alongside that count, not in place of it.
Concentrating cells this way is not free of cost. Cytocentrifugation can distort cell shape and change how cells distribute across the slide, so preparation quality has to be assessed before you trust an identification. Native CSF leukocytes also die and lyse over time once outside the body, and neutrophils are especially fragile, so the interval between collection, receipt, and cytospin preparation is a preanalytic fact that qualifies everything you see afterward, not incidental paperwork.
Infants are not small adults for this purpose. CSF cell counts change across the first 90 days of life, so an adult reference interval must not be applied to a pediatric specimen; a laboratory that reports pediatric CSF needs an age-specific reference range on file. Everything downstream, cell identification, pattern naming, and correlation, assumes you already know whether the preparation in front of you is a fair representation of the specimen as collected.
Read the clock and the reference range before you read the cell, because a cytospin only shows you what survived long enough to be concentrated and stained.
From collection to a reported CSF cytospin differential
Collect
CSF is collected, usually by lumbar puncture, into a clean container; collection time is recorded because it starts the clock on cell survival.
Receive
The laboratory logs receipt time; the collection-to-receipt interval is the first preanalytic fact that will qualify the result.
Count
A separately validated hemocytometer (or equivalent) total nucleated-cell and RBC count is performed on the native specimen before cells are lost to preparation or delay.
Cytocentrifuge and stain
A measured volume is cytocentrifuged to concentrate cells onto a slide, then stained, commonly with Wright-Giemsa or a locally validated Romanowsky-type stain.
Review morphology
Trained personnel assess preparation and cell quality first, then classify the cells present and count a differential when enough intact cells are available.
Correlate and report
The differential is reported with the total nucleated-cell count, RBC count, protein, glucose, microbiology results, and any degeneration or low-cell-number qualifier.
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