The<unk> test (VDRL) is a nontreponemal serological screening for syphilis, the monitoring of the response to therapy, the detection of CNS involvement, and as an aid in the diagnosis of congenital syphilis. The basis of the test is that an antibody produced by a patient with syphilis reacts with an extract of ox heart (diphosphatidyl glycerol). It therefore detects anti-cardiolipin antibodies (IgG, IgM or IgA).
Many other conditions can produce false positive results, including some viruses (mononucleosis, hepatitis), drugs, rheumatic fever, rheumatoid arthritis, lupus, and leprosy. 
The syphilis anti-cardiolipin antibodies are beta-2 glycoprotein independent, where as those that occur in the antiphospholipid antibody syndrome (associated to lupus for example) are beta-2 glycoprotein dependent, and this can be used to tell them apart in an ELISA assay.  This test is very useful as the trend of titres are correlated to<unk>  activity (i.e. falling titres indicate successful treatment). It has a very good sensitivity for syphilis, except in late tertiary form.
FTA-ABS is a far more specific test for syphilis and, in the presence of a positive VDRL test, indicates active infection.
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