Venereal Disease Research Laboratory test: A blood test for syphilis. Venereal Disease Research Laboratory is commonly abbreviated VDRL.
A negative ("nonreactive") VDRL is compatible with a person not having syphilis. However, a person may a negative VDRL and still have syphilis since, in the early stages of the disease, the VDRL often gives negative results. This is called a false negative VDRL.
The VDRL test is sometimes positive in the absence of syphilis. For example, a false positive VDRL can be encountered in infectious mononucleosis, lupus, the antiphospholipid antibody syndrome, hepatitis A, leprosy, malaria and, occasionally, pregnancy.
The RPR (rapid plasma reagin) test is similar to the VDRL test. It is also designed to detect an antibody substance in the bloodstream when syphilis is present but, as with the VDRL, early syphilis infections may give a false negative RPR result. The RPR, like the VDRL, can also give false positive results.