Syphilis Diagnosis Using an Advance Concept for Non-Treponemal Test Development

Today, different laboratory techniques are available for syphilis diagnosis. Among all, serological tests are the most popular because of their ease of use. Serological tests for syphilis diagnosis can be grouped into non-treponemal and treponemal types. The non-treponemal test type includes Venereal Disease Research Laboratory (VDRL) slide test, Unheated Serum Reagin (USR) test, Rapid Plasma Reagin (RPR) test and Toluidine Red Unheated Serum test (TRUST). All detects non-treponemal antibody and were introduced many years back. Still they are use for the syphilis screening in India. Treponemal test detects treponemal specific antibody and are available in different assay formats. Recently, introduction of automated treponemal test had changed the practice for the syphilis diagnosis. Many laboratories are now following reverse practice; automated treponemal test is use first for syphilis screening. Nontreponemal tests are not available in automated format. However, their availability can be very useful in syphilis diagnosis. It is ideal for the huge number of sample study especially in blood bank settings where work load is more. In current study, an attempt was made to develop a nontreponemal test which can be automated. Cardiolipin antigen was modified and coated on microwell surface through an advance concept of covalent attachment. Such antigen coated plate was studied with few syphilis reactive samples in enzyme immunoassay (EIA) format.

It was found out that cardiolipin got attached to microwell surface successfully and showed promising result with end-point titer determination study with syphilis reactive samples. RPR was used as reference test. Both tests demonstrated similar result in their ability to determine the endpoint titer. Further study is required with more number of samples to validate test performance for syphilis diagnosis. Described test can be useful as substitute for currently used nontreponemal tests.