CSF smear

Definition

A cerebrospinal fluid (CSF) smear is a microscopic examination of the clear fluid that moves in the space surrounding the spinal cord and brain. CSF protects the brain and spinal cord from injury.

Alternative Names

Spinal fluid smear; Cerebrospinal fluid smear

Why the Test is Performed

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

How the Test is 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.

How to Prepare for the Test

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

How the Test Will Feel

The laboratory test is painless and does not involve the patient.

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

Risks

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

Normal Results

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

If bacteria are present, that indicates bacterial meningitis. Other kinds of infections might include tuberculosis and fungal infections. Certain bacteria or viruses can also be detected using special tests.