VDRL test is used for-

Laboratory diagnosis of syphilis  Lab. diagnosis of syphilis consists of: - A) Demonstration of spirochetes under microscopy  Microscopy is applicable only in the primary & secondary stage as spirochetes are abundant during the primary, and secondary stage (maximum number of spirochetes and infectivity). Microscopy used are Dark field microscopy, and immunofluorescence microscopy (Direct fluerecent antibody test - DFA-TP). B) Serological tests  These tests form the mainstay of laboratory diagnosis. Serological tests are: - 1) Non-specific tests (reagin antibody or standard tests):- Kahn test, VDRL, Rapid plasma reagin (RPR), automated VDRL-ELISA, Washermann test. These tests measure IgG & IgM against cardiolipin. 2) Group-specific test: - CFT 3) Species-specific tests: - Treponema pallidum particle agglutination (TPPA) test, Treponema pallidum immobilization (TP1), Treponema pallidum hemagglutination assay (TPHA), ELISA.  Specific treponemal tests (FTA-ABS, TPHA, TPI) are of little value as indicators of clinical cure, as they tend to remain positive inspite of Treatment. Nontreponemal tests (eg VDRL) will become nonreactive or will be reactive at lower titers after therapy, so can be used for monitoring patient's response to treatment These tests usually become negative 6-18 months after effective treatment of syphilis  A four-fold or greater decrease in antibody titre indicates a response to therapy