Seroprevalence of syphilis by VDRL test and biological false positive reactions in different patient populations: Is it alarming? Our experience from a tertiary care center in India.

INTRODUCTION

Many centers for sexually transmitted infections in India perform only a single screening assay for diagnosis of syphilis which may yield biological false positive (BFP) reactions.

AIMS AND

OBJECTIVE

The aim of this study was to determine the true picture of seroprevalence of syphilis and BFP reactions in different patient groups.

MATERIALS AND

METHODS

A total of 57,308 serial serum samples obtained over a period of 5 years from different patient groups were screened by venereal disease research laboratory (VDRL) test both qualitatively and quantitatively. VDRL reactive sera were confirmed by Treponema pallidum hemagglutination (TPHA) test.

RESULTS

The overall seroprevalence of syphilis by VDRL test was 1.27%, and BFP rate in test population was 0.14%. The rate of BFP reactions among total tested male (0.44%) and female (0.1%) patients differs significantly. Out of 733 VDRL reactive samples, 81 were BFP, i.e., BFP reaction is occurring at a frequency of 11% of the total VDRL reactive samples (ratio of 8:1 for true positives/BFP). Similarly, among antenatal cases, almost 24% of the total VDRL reactive samples were BFP, or for every 116 true positives, there were 37 (almost one-third) BFP.

CONCLUSION

Although the overall seroprevalence of syphilis is low; the frequency of occurrence of BFP reactions is quite alarming. Hence, treponemal test must be used for confirmation of VDRL reactive sera.