VDRL is a: September 2010, March 2011
Ans. A: Slide flocculation test The VDRL test for syphilis is an example of slide flocculation Venereal Disease Research Laboratory test/ VDRL It is a blood test for syphilis and was developed by the former Venereal Disease Research Laboratory, now the Treponemal Pathogenesis and Immunology Branch, of the United States Public Health Service. Its first iteration being that developed by August Paul von Wasserman with the aid of Albe Neisser in 1906. The RPR (Rapid Plasma Reagin) test uses the same antigen as the VDRL, but in that test it has been bound to several other molecules including a carbon paicle to allow visualization of the flocculation reaction without the need of a microscope. The (VDRL) is a nontreponemal serological screening for syphilis that is also used to assess response to therapy, to detect 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 hea (diphosphatidyl glycerol). It therefore detects anti-cardiolipin antibodies (IgG, IgM or IgA), visualized through foaming of the test tube fluid, or "flocculation". Many other medical conditions can produce false positive results, including some viruses (mononucleosis, hepatitis), drugs, pregnancy, rheumatic fever, rheumatoid ahritis, 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 apa in an ELISA assay. This test is very useful as the trend of titres are correlated to disease activity (i.e. falling titres indicate successful treatment). It has a very good sensitivity for syphilis, except in late teiary form There are a number of treponemal-specific tests such as the Fluorescent treponemal antibody-absorption (FTAABS) test, Treponema pallidum hemagglutination assays (TPHA and MHA-TP), Treponema pallidum paicle agglutination assay (TP-PA), and the Toluidine red unheated serum test (TRUST) which may be used to confirm a positive VDRL result. These tests are more specific for syphilis than non-treponemal tests and, in the presence of a positive test, more likely indicate active infection. Other treponemal infections such as yaws, bejel and pinta and possibly nonpathogenic commensal treponemes can result in a positive. All treponemal specific tests will remain positive for life once a person has been infected with syphilis, even if syphilis has been adequately treated. Therefore, these types of tests cannot be used to monitor the treatment of syphilis.
Slide flocculation test
Tube flocculation test
Gel precipitation test
Indirect hemagglutination test