This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'VDRL test is used for- \nSelect and explain. \nA. Chanchroid, B. LGV, C. Granuloma inguinale, D. Syphilis', 'role': 'user'}, {'content': "Answer: D \nExplanation: Laboratory diagnosis of syphilis\n\n\xa0Lab. diagnosis of syphilis consists of: -\n\nA) Demonstration of spirochetes under microscopy\n\xa0Microscopy is applicable only in the primary & secondary stage as spirochetes are abundant during the primary,\nand secondary stage (maximum number of spirochetes and infectivity). Microscopy used are Dark field microscopy,\nand immunofluorescence microscopy (Direct fluerecent antibody test - DFA-TP). B) Serological tests\n\xa0These tests form the mainstay of laboratory diagnosis. Serological tests are: -\n1) Non-specific tests (reagin antibody or standard tests):- Kahn test, VDRL, Rapid plasma reagin (RPR), automated VDRL-ELISA, Washermann test.\nThese tests measure IgG & IgM against cardiolipin. 2) Group-specific test: - CFT 3) Species-specific tests: - Treponema pallidum particle agglutination (TPPA) test, Treponema pallidum\nimmobilization (TP1), Treponema pallidum hemagglutination assay (TPHA), ELISA.\n\n\xa0Specific treponemal tests (FTA-ABS, TPHA, TPI) are of little value as indicators of clinical cure, as they tend to remain positive inspite of Treatment.\n\nNontreponemal tests (eg VDRL) will become nonreactive or will be reactive at lower titers after therapy,\nso can be used for monitoring patient's response to treatment These tests usually become negative 6-18 months after effective treatment of syphilis\n\xa0A four-fold or greater decrease in antibody titre indicates a response to therapy", 'role': 'assistant'}]