Qualitative evaluation of macroscopic flocculation tests for syphilis

Area of Science:

• Clinical diagnostics
• Microbiology
• Immunology

Background:

• Syphilis diagnosis relies on serological tests to detect antibodies against Treponema pallidum.
• Screening programs utilize rapid, cost-effective tests, but their accuracy requires validation.
• The Venereal Disease Research Laboratory (VDRL) Slide Test is a standard diagnostic method.

Purpose of the Study:

• To evaluate the performance of the Rapid Plasma Reagin (RPR) Card Test and Reagin Screen Test (RST) as screening tools for syphilis.
• To compare the reactivity of RPR and RST with the VDRL Slide Test.
• To assess the confirmation rates of reactive screening tests using the fluorescent treponemal antibody absorption (FTA-ABS) test.

Main Methods:

• A total of 5,202 serum samples were tested concurrently using the RPR Card Test, RST, and VDRL Slide Test.
• Reactive specimens from all three initial tests were subsequently confirmed using the FTA-ABS test.
• Procedural and testing challenges encountered during the study were documented.

Main Results:

• VDRL reactivity was observed in 3.8% (199/5202) of samples, RPR in 3.6% (187/5202), and RST in 3.5% (183/5202).
• FTA-ABS confirmation rates for reactive samples were 58.2% for VDRL, 73.3% for RPR, and 62.8% for RST.
• The study identified specific testing and procedural issues impacting test performance.

Conclusions:

• The RPR Card Test and RST demonstrate moderate agreement with the VDRL test for syphilis screening.
• A significant proportion of reactive screening tests require confirmation by FTA-ABS, highlighting the need for confirmatory testing.
• The findings underscore the importance of addressing testing and procedural challenges for reliable syphilis diagnostics.