A comparative analysis of VDRL, RPR, Immutrep TPHA and Instachk TP

Abstract

INTRODUCTION Syphilis is a systemic
infectious disease caused by Treponema
pallidum which can lead to irreversible lifelong
sequelae if left untreated. Diagnosis
of syphilis today mainly depends on serological
assays each of which have their
own pitfalls. Hence it is essential to evaluate
the present day serological diagnosis
of syphilis and to compare their effectiveness
in diagnosis. AIM To compare RPR,
VDRL, Immutrep TPHA and Instachk TP
MATERIALS AND METHODS This prospective
cohort study was done during the
period of Dec 2010 to June 2011. Serum
samples from four hundred and fifty patients
were obtained from STD department
and antenatal clinic and they were subjected
to RPR, VDRL, Immutrep TPHA
and Instachk TP. RESULTS Overall positivity
rate of serological tests in the detection
of syphilis was VDRL (90.56), RPR
(79.25), TPHA (100) and Instachk TP
(100). VDRL was able to detect 6 cases of
low titres more frequently than RPR. RPR
was one titre less than VDRL in eight
cases. Instachk TP was as specific as
TPHA but the results can
be interpreted within 15 minutes and can
be done at field level. CONCLUSION
VDRL detects low titres more frequently
than RPR.VDRL and RPR should not be
interchanged during follow up of patients
and in external quality assessment.
Among the specific tests, the Instachk test
is a rapid test that can be interpreted
within minutes. This can open up new
avenues for early, rapid and accurate detection
of syphilis at a field level. So the
present day serological tests of syphilis
can thus be limited to the specific tests to
exclude syphilis and the nonspecific tests
to judge the need or effectiveness of antisyphilitic
treatment.