Introduction:
Syphilis, the first transfusion-transmitted disease
described, was reported commonly before 1950. Screening
of blood donors have been performed with serological test
from the early of stages of blood transfusion practices..
Although the risk the transmission of syphilis through
blood is negligible, in India, it is mandatory that blood
banks screen every donation for syphilis3
. The study was
performed to evaluate the true seroprevalence of syphilis
in blood donors as well as to evaluate the suitability of
Immunochromatographic test, PaGIA, TPHA and ELISA
as replacement for RPR either for screening or
confirmation of syphilis in blood donors.
Material & Methods:
The total number of donors who were screened for
syphilis were 28,544. All the donors were screened for
HIV-1, 2, Hepatitis B, Hepatitis C, syphilis and malaria.
Rapid plasma reagin (RPR) method was done as a primary
screening method of syphilis using carbogen particles
(Tulip laboratories). A total of 132 RPR positive and 132
RPR negative control sera were included in the study to
compare the additional test performed.
Results:
Out of the total samples tested , 132 donors were
found to be RPR reactive with 0.46% seropositivity. The
seroprevalence was 0.46% (n= 127) among male donors
and 0.43% (n =05) in female donors which was not
statistically significantly different (p>0.05). The sensitivity,
specificity, PPV, and NPV of treponemal tests was done
and it was seen that PaGIA, ICT, and ELISA had
sensitivity of 100%, 98.8% and 100%, respectively and
the specificity of PaGIA, ICT, and ELISA was found to be
78.7%, 97.8%, and 93.5%. An overall agreement of 91.6 %
was found in all four treponemal tests.
Conclusion:
On comparing the RPR titer with other treponemal
tests performed, it was found that titer >16 gave the good
prediction of positive treponemal tests. Other studies have
also shown correlation of RPR or VDRL titre with
treponemal tests. In our study, the sensitivity of ELISA,
TPHA and PaGIA were similar and comparable. The
positive predictive value and negative predictive values
for PaGIA were 89.4% and 100%, respectively. In our
study, treponemal assay had higher specificity than
cardiolipin assay. The number of false positive samples can
be reduced by using a method for screening which has
higher specificity.