Literature review > Issue 8 > Review on Diaz et al. 

Several rapid lateral flow (immunochromatographic strip) tests for the serological diagnosis of syphilis have been developed and commercialized, including the Abbott Determine Rapid Syphilis TP [1]. These tests are relatively simple to use and interpret and results can usually be obtained in a few minutes. They utilize plasma, serum, or even whole finger-stick blood as specimens and were developed to meet the need for near-patient testing, since field use of syphilis screening tests are often unreliable [2]. Rapid lateral flow tests can be used where standard laboratory facilities are lacking, transport of specimens from clinics to laboratories are poor, and when same-day results are needed to provide appropriate therapy to patients. Such rapid and simple tests may therefore offer potential advantages, especially in developing countries and in other resource-limited settings. However, there are limitations to these rapid tests. They detect antibodies only to specific Treponema pallidum antigens and therefore closely correlate with the results of syphilis confirmatory tests such as TPHA or TPPA. Unlike RPR screening tests, the rapid lateral flow tests will usually produce positive results in patients with past, treated disease as well as those with active infection [3]. As a result, they may be more useful for use in low-prevalence populations such as antenatal clinics and not as useful in higher prevalence settings such as STD clinics [4].

This report establishes a close correlation between the results of the Determine TP test compared with a reference TPHA method using a panel of archived positive and negative sera that were tested under ideal conditions. The correlation between the rapid tests and TPHA may not be as close in a prospective clinical study performed in the field under less ideal conditions, or when whole blood is used as a specimen. Three lab and clinical personnel separately interpreted the results, resulting in a small number of specimens variably read as either positive or negative. This inter-reader variability was minimal, indicating the test was relatively easy to read. Discrepant results may be resolved with further training of readers or by re-testing. Another encouraging result was that no significant difference in sensitivity or specificity for this test was reported when sera from HIV-seropositive and HIV-seronegative individuals were evaluated, indicating this test can be used in high HIV-endemic regions.

Since this study only evaluated archived, well-characterized sera, the authors suggest that additional studies are needed to establish their value in routine applications. There is now an increasing body of evidence from field and clinical studies in developing world populations suggesting that the current rapid tests for syphilis are useful [5-8]. However, there have also been calls for development of a new generation of rapid tests whose results more closely correlate with cardiolipin-based screening tests so that persons with active infections in high-risk settings or highly endemic areas can be more reliably detected [4,9].

Literature Cited

1. Sexually Transmitted Diseases Diagnostics Initiative (SDI). Laboratory-based Evaluation of Rapid Syphilis Diagnostics, Manual of Operations. UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland

2. Majoko F, Munjanja S, Nystrom L, Mason E, Lindmark G. Field efficiency of syphilis screening in antenatal care: lessons from Gutu District in Zimbabwe Cent Afr J Med. 2003;49:90-3.

3. Zarakolu P, Buchanan I, Tam M, Smith K, Hook EW 3rd. Preliminary evaluation of an immunochromatographic strip test for specific Treponema pallidum antibodies..J Clin Microbiol. 2002; 40:3064-5

4. West B, Walraven G, Morison L, Brouwers J, Bailey R. Performance of the rapid plasma reagin and the rapid syphilis screening tests in the diagnosis of syphilis in field conditions in rural Africa. Sex Transm Inf 2002; 78:282-285

5. Gloyd S, Montoya P, Floriano F, Sherr K, Sairosse J. Syphilis Screening in Pregnancy: Improving Coverage using Rapid ICS Tests in Mozambique. American Public Health Association 133rd Annual Meeting 2005, Abstract #112893

6. Goel N, Sharma M, Gupta N, Sehgal R. Rapid Immunochromatographic Test for Syphilis. Indian J Med Micro 2005, 23:142-143 Qualpro test

7. Siedner M, Zapitz V, Ishida M, De La Roca R, Klausner JD. Performance of rapid syphilis tests in venous and fingerstick whole blood specimens. Sex Transm Dis. 2004; 31:557-60.

8. Sato NS, de Melo CS, Zerbini LC, Silveira EP, Fagundes LJ, Ueda M. Assessment of the rapid test based on an immunochromatography technique for detecting anti-Treponema pallidum antibodies. Rev Inst Med Trop Sao Paulo. 2003 Nov-Dec; 45(6): 319-22. Epub 2004.

9. Peeling RW, Ye H. Diagnostic tools for preventing and managing maternal and congenital syphilis: an overview. Bull World Health Organ. 2004;82:439-46.

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