CSF smear

A cerebrospinal fluid (CSF) smear is an exam of the fluid that moves in the space around the spinal cord and brain. CSF protects the brain and spinal cord from injury.

How is the Test Performed?

A sample of CSF fluid is needed. This is usually done with a lumbar puncture. For information on how this procedure is performed, see spinal tap.

The sample is sent to a laboratory, where a tiny amount is spread on a glass slide. A member of the laboratory team looks at the sample under a microscope. The smear shows the color of the fluid and the number and shape of cells present in the fluid. Other tests, such as a Gram stain, may be done to check for bacteria.

Preparation for the Test

For information on how to prepare for the procedure to obtain the CSF sample, see spinal tap.

How will the Test Feel?

The laboratory test is painless and does not involve you.

For information on how it will feel to have a sample of CSF fluid removed, see spinal tap.

Why is the Test Performed?

The test is done to check for signs of infection in a sample of CSF.

What Abnormal Results Mean

Bacteria or other germs in the sample may be a sign of:

• Bacterial meningitis
• Fungal infections
• Tuberculosis

Some bacteria or viruses can also be detected using special tests.

CSF smear Risks

A laboratory smear poses no risk. For risks from the procedure done to get a CSF sample, see spinal tap.

References

Griggs RC, Jozefowicz RF, Aminoff MJ. Approach to the patient with neurologic disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 403.

Swartz MN, Nath A. Meningitis: bacterial, viral, and other. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 420.

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