Abstract
BackgroundSyphilis causes up to 1,500,000 congenital syphilis cases annually. These could be prevented if all pregnant women were screened, and those with syphilis treated with a single dose of penicillin before 28 weeks gestation. In recent years, rapid point-of-care tests have allowed greater access to syphilis screening, especially in rural or remote areas, but the lack of quality assurance of rapid testing has been a concern. We determined the feasibility of using dried blood spots (DBS) as specimens for quality assurance of syphilis serological assays.MethodsWe developed DBS extraction protocols for use with Treponema pallidum particle agglutination assay (TPPA), Treponema pallidum haemagglutination assay (TPHA) and an enzyme immunoassay (EIA) and compared the results with those using matching plasma samples from the same patient.ResultsSince DBS samples showed poor performance with TPHA and EIA (TPHA sensitivity was 50.5% (95% confidence interval: 39.9–61.2%) and EIA specificity was 50.4% (95% CI: 43.7–57.1%), only the DBS TPPA was used in the final evaluation. DBS TPPA showed an sensitivity of 95.5% (95% CI: 91.3–98.0%) and a specificity of 99.0% (95% CI: 98.1–99.5%) compared to TPPA using plasma samples as a reference.ConclusionDBS samples can be recommended for use with TPPA, and may be of value for external quality assurance of point-of-care syphilis testing.
Highlights
Syphilis causes up to 1,500,000 congenital syphilis cases annually
Phase 1: Preliminary evaluation of different syphilis serological methods with dried blood spots (DBS) samples During the first phase of the project, protocols for DBS samples were developed for Treponema pallidum particle agglutination assay (TPPA), (DBS TPPA) Treponema pallidum haemagglutination assay (TPHA) (DBS TPHA) and enzyme Immunoassay (EIA) (DBS EIA). 464 DBS samples were tested with TPPA, TPHA, and EIA
As prenatal screening for syphilis using point-of-care tests (POCT) becomes widely implemented, an external quality assurance (EQA) method appropriate for use with blood collected by a finger prick must be developed to assure the proficiency of POC testing in rural or remote areas
Summary
Syphilis causes up to 1,500,000 congenital syphilis cases annually. These could be prevented if all pregnant women were screened, and those with syphilis treated with a single dose of penicillin before 28 weeks gestation. It is estimated that the burden of congenital syphilis is large, with 1.5 million cases per year worldwide [1] These could be prevented if all pregnant women were screened and treated with a single dose of benzathine penicillin before 28 weeks gestation [2]. Syphilis testing is usually done using laboratory based assays such as Treponema pallidum haemagglutination assay (TPHA), Treponema pallidum particle agglutination assay (TPPA), rapid plasma reagin (RPR), or enzyme Immunoassay (EIA) These tests need to be used with serum or plasma samples and require a centrifuge, shaker, and refrigeration for the reagents. The objectives of this study were to develop and validate DBS protocols for use with commercially available syphilis diagnostic assays, and to determine their performance in syphilis serological assays using plasma samples as a reference
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