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Original article
An immunofiltration device for the simultaneous detection of non-treponemal and treponemal antibodies in patients with syphilis
  1. A R Castro1,2,
  2. H C Mody2,
  3. S Y Parab3,
  4. M T Patel3,
  5. S E Kikkert1,
  6. M M Park4,
  7. R C Ballard1
  1. 1Centers for Disease Control and Prevention, Division of STD Prevention, Atlanta, Georgia, USA
  2. 2Institute of Medical Technology, Surat, India
  3. 3Span Diagnostics Ltd, Surat, India
  4. 4Georgia Department of Community Health, Atlanta, Georgia, USA
  1. Correspondence to Dr A R Castro, Centers for Disease Control and Prevention, 1600 Clifton Road, MS A-12, Atlanta, GA 30333, USA; acastro{at}


Objective The development of a rapid immunofiltration (flow-through) test for the simultaneous detection of non-treponemal and treponemal antibodies in the serum of patients with syphilis.

Methods The assay is rapid, inexpensive, and requires limited expertise in interpreting the results. The test is based on the principle of immunofiltration, with two antigens and control material spotted on the membrane of a through-flow device. A positive test is characterised by the appearance of three red/magenta spots within 2–10 min.

Results A total of 376 banked serum samples obtained from the Georgia Public Health Laboratory was examined by the flow-through test, the rapid plasma reagin (RPR) test and the Treponema pallidum passive particle agglutination assay (TPPA). The sensitivity and specificity of the non-treponemal spot were 96.5% and 97.7%, respectively, when compared with the RPR test, and the sensitivity and specificity of the treponemal test spot were 97.3% and 99.1% when compared with the TPPA test. In addition, the test yielded equivalent results to those obtained in comparator tests when 104 sera from cases of syphilis of known stage, 49 sera from diseases other than syphilis and 23 sera known to exhibit biological false-positive reactions were tested in parallel.

Conclusions These results indicate that the dual treponemal and non-treponemal assay could be used as a screen and confirmatory test for the serological diagnosis of syphilis in remote or resource-poor settings where there is a need to provide counselling and treatment at the initial consultation.

  • Serology
  • syphilis
  • Treponema pallidum

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  • Funding The Centers for Disease Control and Prevention (CDC) provided financial support for this study in the form of allowing the principal investigator to devote time, materials and effort for the development of a non-treponemal antigen suitable for attachment to a solid support. This effort culminated in the filing of a US and international patent application no 1200700496 titled ‘Methods, Immunoassays and Devices for Detection of Anti-lipodal Antibodies’. Through a cooperative research and development agreement, Span Diagnostics obtained a licence agreement from CDC to utilise the principles of the invention to develop a working prototype. Span Diagnostics funded the developmental phase of the final commercial product.

  • Competing interests Span Diagnostics will market the rapid test developed cooperatively with CDC under a cooperative research and development agreement. ARC through a technology transfer agreement between CDC and Span Diagnostics may receive residuals as the inventor for the use of the CDC patent ‘Methods, Immunoassays and Devices for Detection of Anti-lipodal Antibodies’ US Patent Application Publication no 2009/0263825 A1.

  • Ethics approval This study was performed on archived sera from which all patient identifiers had been removed. Protocols for studies using these sera for the development of new serological test for syphilis were reviewed by the institutional review board of the CDC (protocol no 2018) and determined to be exempt from further review.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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