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A
recombinant-antigen enzyme immunoassay showed sensitivity and
specificity comparable to the T. pallidum hemagglutination
test for the confirmation of syphilis.
Comparison of
a recombinant-antigen enzyme immunoassay with Treponema pallidum
hemagglutination test for serological confirmation of syphilis.
Rodriguez I, Alvarez EL, Fernandez C, Miranda A.
Mem Inst Oswaldo Cruz.
2002;97:347-349.
Summary:
Question
What is the performance of a recombinant-Tmp-A antigen EIA (commercially
available in Cuba) compared to the T. pallidum hemagglutination
assay for the serological confirmation of syphilis?
Design
This study describes a direct comparison of
a micro-EIA using the recombinant T. pallidum antigen Tmp-A versus
the T. pallidum hemagglutination test for the detection of T.
pallidum specific antibodies in sera from different groups of
patients.
Participants
Three hundred sixty-seven sera from patients
in Cuba with primary (n = 38), secondary (n = 10), early latent (n = 28),
and congenital (n = 2) syphilis, from patients with other infectious
diseases (n = 56), from patients with autoimmune diseases (n = 31), and
from elderly (n = 9), pregnant (n = 29), and normal blood donors (n = 164)
were tested. Patient selection criteria were not described.
Description of Tests and Diagnostic
Standard
All sera were tested with the VDRL or RPR
nontreponemal tests, a micro-EIA using as antigen the protein Tmp-A,
obtained by synthesis to high levels in E. coli (BioSCREEN anti-T.
pallidum, Heber Biotec S. A., Cuba), and with the TPHA test (OXOID
Diagnosis Reagents, England), according to the manufacturer's
instructions.
Main Outcome Measures
The sensitivity, specificity, positive
predictive value (PPV), and negative predictive value (NPV) of the
micro-EIA assay for the diagnosis of syphilis as determined by clinical
diagnosis were calculated.
Main Results
The results of the different serological tests applied to the groups
of sera are shown in the table. Of 367 sera, 95 were positive by VDRL, or
RPR, or both. Of these 95, 75 were confirmed positive by TPHA; 83 were
positive by EIA; 12 were EIA positive but TPHA negative; and 4 (all from
patients with early latent syphilis) were TPHA positive but EIA negative.
The anti-Tmp-A EIA and the TPHA agreed in 349 (95.1%) of sera. Of 18 sera
reactive by non-treponemal tests but not by TPHA, 15 were non-reactive and
3 were reactive by the anti-Tmp-A EIA. The calculated sensitivity,
specificity, PPV, and NPV of the EIA were 93.3%, 95.5%, 84.3%, and 98.2%,
respectively.
| Results
of serological tests for syphilis on selected groups of sera |
| Group |
Number
of specimens |
Number
with positive result by test |
| VDRL
or RPR |
TPHA |
EIA |
| Primary
syphilis |
38 |
37 |
35 |
34 |
| Secondary
syphilis |
10 |
10 |
10 |
10 |
| Early latent
syphilis |
28 |
28 |
28 |
24 |
| Congenital
syphilis |
2 |
2 |
2 |
2 |
| Infectious
disease |
56 |
6 |
0 |
4 |
| Autoummune
disease |
31 |
5 |
0 |
1 |
| Elderly |
9 |
2 |
0 |
1 |
| Pregnant |
29 |
3 |
0 |
0 |
| Normal blood
donor |
164 |
2 |
0 |
6 |
Authors' Conclusions
In this set of heterogeneous sera, this Tmp-A
EIA was viewed as less subjective than the TPHA test, but comparable in
sensitivity and specificity.
Source of funding: None given
For correspondence: Islay Rodriguez,
Departamento de Bacteriologia-Micologia, Instituto Pedro Kouri, Casilla
Postal 601, Marianao 13, Ciudad de La Habana, Cuba. E-mail address: islay@ipk.sld.cu
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