The CSF-VDRL test is used to help diagnose neurosyphilis. It looks for substances called reagins, which are sometimes produced by the body in reaction to the syphilis-causing bacteria.
Venereal disease research laboratory slide test - CSF
A sample of spinal fluid is needed. For information on how this is taken, see: Lumbar puncture (spinal tap)
The CSF-VDRL test is done to diagnose syphilis in the brain or spinal cord. Brain and spinal cord involvement is usually a sign of late stage syphilis.
Blood screening tests (VDRL and RPR) are better at detecting middle stage (secondary) syphilis.
A negative result is normal.
However, false-negatives can occur. This means you can have syphilis even if this test is normal. Therefore, a negative test does not always rule out the infection. Other signs and tests may be used to diagnose neurosyphilis.
A positive result is abnormal and is a sign of neurosyphilis.
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Workowski KA, Berman S. Centers for Disease Control and Prevention (CDC). Sexually transmitted diseases treatment guidelines, 2010. MMWR Recomm Rep. 2010 Dec 17;59(RR-12):1-110.
Hook EW III. Syphilis. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 327.