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 the Test is Performed
A sample of CSF fluid is needed. This is usually done with a lumbar puncture. This is called a 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 or fungal wet prep, may be done to check for bacteria or fungi.
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 you.
For information on how it will feel to have a sample of CSF fluid removed, see spinal tap.
Why the Test is 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
Some bacteria or viruses can also be detected using special tests.
A laboratory smear poses no risk. For risks from the procedure done to get a CSF sample, see spinal tap.
Spinal fluid smear; Cerebrospinal fluid smear
Griggs RC, Jozefowicz RF, Aminoff MJ. Approach to the patient with neurologic disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 403.
Swartz MN, Nath A. Meningitis: bacterial, viral, and other. In: Goldman L, Schafer AI, eds. Golsman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 420.
Update Date 8/31/2014
Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.