A new recombinant antigen latex agglutination test (Syphilis Fast) for the rapid serological diagnosis of syphilis.
We report an assessment of Syphilis Fast, a new latex test that uses a pool of 3 recombinant Treponema pallidum antigens (TpN15, TpN17, and TpN47) for the serodiagnosis of syphilis. Specificity was evaluated by screening 1518 unselected blood specimens in parallel with Syphilis Fast, the Captia SelectSyph-G EIA and the Venereal Disease Research Laboratory (VDRL) cardiolipin antigen test while sensitivity was tested using a panel of 99 treponemal sera (treated and untreated) representing various stages of infection and 15 treponemal sera detected on screening. The specificity of Syphilis Fast on initial testing (99.8%) was significantly higher (P<0.02) than that of Captia SelectSyph-G (99.2%) and the VDRL (99.1%): the specificity of Syphilis Fast remained significantly higher (P<0.02) after repeat testing (respective values 99.9%, 99.5% and 99.4%). There was no difference in the sensitivity of Syphilis Fast and Captia SelectSyph-G on initial (93% vs 92.1%) or repeat (95.6% vs 94.7%) testing: both were significantly more sensitive (P<0.001) than the VDRL (46.5% on initial and 43.9% on repeat testing). The sensitivities of the Treponema pallidum haemagglutination test (TPHA) and FTA-abs were 98.2% and 95.6% respectively. Negative reactions in Syphilis Fast and SelectSyph-G were associated with treated infections and correlated with low TPHA titres (< or = 80). We conclude that Syphilis Fast is a highly specific, simple and fast screening test with a sensitivity comparable to native antigen treponemal tests and that it merits consideration as a front-line screening test.
Young
H
H
Department of Medical Microbiology, Edinburgh University Medical School, UK.
Moyes
A
A
de Ste Croix
I
I
McMillan
A
A
D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology; D005069:Evaluation Studies as Topic; D006801:Humans; D007841:Latex Fixation Tests / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D011994:Recombinant Proteins / Q000276:immunology; D012680:Sensitivity and Specificity; D013588:Syphilis Serodiagnosis / Q000379:methods*; D013997:Time Factors; D014210:Treponema pallidum / Q000276:immunology
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D011933:Reagent Kits, Diagnostic; D011994:Recombinant Proteins