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An
immunochromatographic strip test for the qualitative detection of T.
pallidum specific antibodies agreed 100 % with the results of the
FTA-ABS test in a preliminary evaluation.
Preliminary
evaluation of an immunochromatographic strip test for specific Treponema
pallidum antibodies.
Zarakolu P, Buchanan
I, Tam M, Smith K, Hook EW III.
Journal of Clinical
Microbiology 2002;40:3064-3065.
Summary:
Question
What is the performance of an immunochromatographic strip test (ICS)
compared to those of the standard RPR and FTA-ABS assays for the
qualitative detection of serum antibodies to T. pallidum?
Design
This study describes a blinded, direct comparison of a new
immunochromatographic strip test and a commercial FTA-ABS test, using
serum samples screened by RPR, for serological testing for syphilis.
Participants
Thirty serum samples collected at the time of diagnosis and 171 samples
collected for up to 12 months following treatment from 30 patients with
syphilis; 15 sera from 15 patients with false-positive RPR test results;
and 137 sera consecutively collected from 112 patients attending a
Department of Health sexually transmitted disease clinic were analyzed.
Description of Tests and Diagnostic
Standard
The ICS test is a nitrocellulose strip containing an immobilized line of
recombinant 47-kDa T. pallidum antigen, a second line of anti-human
IgG that serves as a positive control, and colloidal gold signal reagent.
The assays were performed at room temperature using 65 ml of sera, and
read after 8 minutes. A positive reaction was defined as the appearance of
two lines on the strip, and a negative reaction was defined as the
appearance of only the control line. All sera were also tested by the
Macro-Vue RPR test (Becton Dickinson Microbiology Systems, Cockeysville,
MD) and the FTA-ABS indirect fluorescent-antibody test (Zeus Scientific,
Inc., Raritan, NJ), as described in the manufacturers' instructions.
Main Outcome Measures
The results of the ICS test compared to the results of the RPR and FTA-ABS
tests were determined.
Main Results
Agreement between the ICS and FTA-ABS test results was 100%. Among the 30
patients with syphilis, the 30 samples collected at diagnosis were
positive by all 3 serological tests, and of the 171 sera collected
following treatment, 140 were positive by RPR and 169 were positive by the
FTA-ABS and the ICS. Of the 15 patients with false-positive RPR, all were
negative by the FTA-ABS and the ICS. Of the 137 sera collected from 112
consecutive clinic patients, the FTA-ABS and ICS tests were positive for
13. Five of these 13 and an additional 7 of the 124 FTA-ABS and ICS
negative sera were RPR positive.
Authors' Conclusions
The ICS test, by providing accurate results
rapidly and without the need for laboratory equipment, has the potential
to contribute to serological screening that is performed as part of
syphilis control efforts, especially in settings where the prevalence of
previously treated syphilis is low.
Source of funding: USAID HealthTech:
Technologies for Health Program
For correspondence: Edward Hook III,
University of Alabama at Birmingham, 703 19th St. S., ZRB 242, Birmingham,
AL, 35294-0007. E-mail address: ehook@uab.edu.
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