USE OF TPHA AND VDRL IN THE DIAGNOSIS OF SYPHILIS

Abstract

INTRODUCTION: Venereal Disease Research Laboratory (VDRL) test is performed by the physicians to screen patients for syphilis and is still the most commonly used test all over the world for screening. Three basic methods has been described in screening for syphilis. These include direct observation of the T. pallidum by dark field microscopy, and nontreponemal and treponemal serologic antibody studies. Nonspecific (non tremonemal) tests like  Venereal Disease Research Laboratory (VDRL) test use lipoidal antigens containing cardiolipin, lecithin, and cholesterol, that flocculate with IgM and IgG. Positive tests occur from 21 days of exposure till about up to 6 weeks after infection. Serologic tests in syphilis only provide indirect evidence of syphilis and may be reactive in the absence of clinical or epidemiologic evidence of syphilis. The reactivity in these cases is usually in low dilutions (<1:8), however, in exceptional cases false reactivity is shown in very high titers up to 1:256. False-positive reactions can also also be seen with treponemal tests. MATERIAL AND METHODS: A total of 10253 patients were tested for syphilis by VDRL as a screnning test during study period. Both the the qualitative and quantitative VDRL tests were done as per the manufacturer's instructions. TPHA was performed on all the sera demonstrating reactivity with VDRL test. VDRL test was based on the principle that after syphilis infection, host develops nontreponemalantilipoidal antibodies in response to the release of lipoidal material from the damaged host cells. Also host produces antibodies against T. pallidum. In TPHA Agglutination of cells shows a positive reaction. In the absence of antibody i.e. in negative cases cells settled down to form a compact button in the well which constituted a negative reaction. RESULTS: In this study a total of 10253 patients were screened for syphilis by VDRL of which 98 were reactive. In a sample of 98 VDRL reactive patients, 33(34%) were males and 65(66%) females. The age of patients who tested VDRL positive in our study ranged from youngest being 21 years to eldest being 66 years. Majority of patients i.e. 88.8% belonged to 20-50 years of age group, with majority of patients 37.75% belonging to age group 30 – 40. CONCLUSION: VDRL test is the best screening test for the diagnosis of syphilis but whenever the patient is serologically reactive it should be confirmed by the more specific TPHA test.