A Preliminary Evaluation of a Prototype Western Blot Confirmatory Test Kit for Syphilis

Abstract

A prototype Western blot kit was evaluated as a confirmatory test for syphilis using 131 sera characterized by other serological tests for syphilis. There were 114 treponemal sera (including 94 cases of early syphilis, 83 of which were untreated) and 17 non-treponemal problem sera (11 gave false positive reactions on screening with the TmpA recombinant antigen enzyme immunoassay (EIA), 3 gave false positive fluorescent treponemal antibody absorbed (FTA-abs) tests, and 3 false positive Captia Syphilis G EIA results). Based on the manufacturer's criteria of reactivity in multiple bands for designating a positive result the Western blot test gave a sensitivity of 99.1% (113/114) and a specificity of 88.2% (15/17) when indeterminate reactions were scored positive and 98.2% (112/114) and 100% (17/17) when indeterminate reactions were scored negative. Sensitivity was high in both treated and untreated infection. Corresponding sensitivities for the TPHA and FTA-abs when equivocal reactions were scored negative were 97.5% (111/114) and 99.1% (113/114). The high sensitivity of the FTA-abs in this study is probably due to the large number of untreated primary infections. Our results with the Western blot, confirm earlier studies using 'in-house' test systems and, support a role for a commercial Western blot test in the confirmatory diagnosis of syphilis. Further studies are required to confirm the high specificity and sensitivity of the kit in a larger series including a wider variety of non-treponemal cases as well as patients with untreated and treated infection.

Western Immunoblotting with FiveTreponema pallidumRecombinant Antigens for Serologic Diagnosis of Syphilis

“…The WB technique based on whole-T. pallidum-cell lysate has been widely used in past years (5,6,10,12,17,28,30,49), and it has been shown to be a reliable confirmatory test (4). Few data are available on the use of recombinant-antigenbased immunoblotting in the diagnosis of syphilis.…”

“…The Western blot (WB) method has been used for the last 15 years to investigate the immune response to individual Treponema pallidum antigens in sera from experimentally infected animals (1,16,25,26,43,46) and from humans with naturally occurring syphilis (4,5,6,10,17,28,30,40,47,49). This method has been proposed as a possible alternative to either FTA-ABS or MHA-TP for the confirmation of the serological diagnosis of syphilis.…”

Evaluation of the fluorescent treponemal antibody absorption test for detection of antibodies (immunoglobulins G and M) to Treponema pallidum in serologic diagnosis of syphilis

“…The T. pallidum WB is also used as an alternative confirmatory test to improve sensitivity and specificity, but indeterminate and false-positive reactivity patterns have been reported. 7,8,15,22,[27][28][29] It was reported that there is over 95% agreement between the WB and the FTA-ABS test for clinically defined syphilis specimens. In a study, 10 WB results were compared with TPPA and FTA-ABS tests, and the sensitivity of the WB, TPPA and FTA-ABS were all reported at 100% and the specificity were 100%, 100% and 94.5%, respectively.…”

Laboratorial Diagnosis of Syphilis

“…It is generally agreed that detection of antibodies to immunodeterminants with molecular masses of 15, 17, 44.5 and 47kDa (TpN15, TpN17, TpN44.5 and TpN47) are diagnostic for acquired syphilis. The Tp-WB showed a high sensitivity in both, treated and untreated infection (Young et al, 1994). One study found that the 17 kDa antigen have the best combined attributes of sensitivity and specificity for diagnostic of syphilis (George et al, 1998).…”