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Original research
Seroconversion in syphilis screening without positive confirmatory tests points at early infection
  1. Silvia Achia Nieuwenburg1,2,
  2. Vita Willemijn Jongen1,3,
  3. Maarten Schim van der Loeff1,2,4,
  4. Henry de Vries1,2,5,
  5. Alje van Dam1,6
  1. 1 Department of Infectious Diseases, Public Health Service Amsterdam, Amsterdam, the Netherlands
  2. 2 Amsterdam UMC location University of Amsterdam, Amsterdam Institute for Infection and Immunity, Meibergdreef 9, Amsterdam, the Netherlands
  3. 3 Stichting HIV Monitoring, Amsterdam, the Netherlands
  4. 4 Amsterdam UMC location University of Amsterdam, Department of Internal Medicine, Division of Infectious Diseases, Amsterdam, Meibergdreef 9, Amsterdam, the Netherlands
  5. 5 Amsterdam UMC location University of Amsterdam, Department of Dermatology, Meibergdreef 9, Amsterdam, Amsterdam UMC location University of Amsterdam, Department of Dermatology, the Netherlands
  6. 6 Amsterdam UMC location University of Amsterdam, Department of Medical Microbiology, Amsterdam Health Service, Mebergdreef 9, Amsterdam, the Netherlands
  1. Correspondence to Silvia Achia Nieuwenburg, Amsterdam UMC location University of Amsterdam, Amsterdam institute for Infection and Immunity, Meibergdreef 9, Amsterdam, the Netherlands; s.a.nieuwenburg{at}amsterdamumc.nl

Abstract

Introduction The chemiluminescence immunoassay (CLIA) is a widely used screening test for syphilis. A CLIA seroconversion in the absence of a positive line immunoassay (LIA) or rapid plasma reagin (RPR) could indicate either an early incubating syphilis or a false positive result. We aimed to evaluate the diagnostic value of such seroconversions.

Methods We retrospectively analysed data of clients visiting the Centre for Sexual Health Amsterdam between July 2013 and August 2021 with a positive CLIA and a negative RPR and negative or indeterminate LIA (at time To), and a preceding visit (T−1) with a negative CLIA <6 months of To (‘unconfirmed CLIA seroconversion’). If available, data of follow-up visits (T1) <2 months of To were also included. A syphilis diagnosis was confirmed if darkfield microscopy or PCR for Treponema pallidum was positive at T0 or T1, or if RPR and/or LIA were positive at T1.

Results We included data of 107 clients with unconfirmed CLIA seroconversion. The value of CLIA seroconversion could not be established in 13 (12.1%) clients. In the remaining 94 clients, the unconfirmed CLIA seroconversion was confirmed as early syphilis in 72 (76.6%) clients and probable syphilis in 6 (6.4%) clients. In 16 (17.0%) clients, the unconfirmed CLIA seroconversion was regarded as a false positive reaction of whom 4 (5.3%) clients had a seroreversion of the CLIA at T1.

Conclusion The majority of unconfirmed CLIA seroconversions represented early syphilis infections. Therefore, additional T. pallidum PCR, a follow-up consultation or early treatment is recommended.

  • SYPHILIS
  • SEXUAL HEALTH
  • Serologic Tests

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

https://doi.org/10.1136/sextrans-2023-055973

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    Data availability statement

    All data relevant to the study are included in the article or uploaded as supplementary information.

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    Footnotes

    • Handling editor Apostolos Beloukas

    • Contributors None.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

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

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.