Treponema pallidum hemagglutination assay seroreactivity among healthy Indian donors and its association with other transfusion transmitted diseases.

BACKGROUND: The aim of the present study was to determine the prevalence of syphilis infection by Treponema pallidum hemagglutination assay (TPHA) among blood donors in Delhi and to study their correlation with other markers of transfusion transmitted infections such as hepatitis C virus (HCV), human immunodeficiency virus (HIV) and hepatitis B surface antigen (HBsAg) so as to establish the utility of TPHA over and above venereal diseases research laboratory test (VDRL), not only as a marker for testing T. pallidum infection, but also as a marker of high risk behavior.

MATERIALS AND METHODS: This prospective study was carried out in the Regional Blood Transfusion Centre, Lady Hardinge Medical College and associated Sucheta Kriplani Hospital, New Delhi for a period of 2 years. Donated blood was screened for TPHA seroreactivity along with screening for anti HIV I and II, anti-HCV, HBsAg by third generation enzyme-linked immunosorbent assay test. A total of 8082 serum samples of blood donors were collected from healthy blood donors in our blood bank. They were classified into two groups- test group and control group based on TPHA positivity. The co-occurrence of HBsAg, HIV and HCV infection were determined in TPHA positive blood donors (test group) in comparison with TPHA negative blood donors (control group).

RESULTS: We found the TPHA seroreactivity to be 4.4% in Delhi's blood donors. Nearly 8.2% (663/8082) of the donated blood had serological evidence of infection by at least one pathogen (syphilis/HIV/hepatitis B virus/HCV) and 6.63% (44/663) donors with positive serology had multiple infections (two or more). Quadruple infection was seen in one donor, triple infection was seen in three donors and double infection was seen in 40 donors. Prevalence of HIV seroreactivity was found to be statistically significant and HCV seroreactivity statistically insignificant in TPHA positive group in comparison to TPHA negative group.

DISCUSSION: In our study, the TPHA seropositivity correlated with higher HIV and HCV seropositivity and the same correlation has been observed by several other studies also. In view of these observations, we propose that testing for syphilis by more sensitive and specific treponemal markers like TPHA rather than VDRL, rapid plasma reagin tests; as TPHA also has the added advantage of picking up all the high risk donors, whereas, VDRL picks up only currently infected donors. Moreover, TPHA should be continued as a marker of high risk behavior especially in high prevalence areas like India where we don't have universal access to markers like nucleic acid amplification technique.