Evaluation of a Rapid Diagnostic Test for Yaws Infection in a Community Surveillance Setting

Abstract

Yaws is a non-venereal treponemal infection caused by Treponema pallidum ssp. pertenue. The WHO has launched a worldwide control programme, which aims to eradicate yaws by 2020. The development of a rapid diagnostic test (RDT) for serological diagnosis in the isolated communities affected by yaws is a key requirement for the successful implementation of the WHO strategy. We conducted a study to evaluate the utility of the DPP test in screening for yaws, utilizing samples collected as part of a community prevalence survey conducted in the Solomon Islands. 415 serum samples were tested using both traditional syphilis serology (TPPA and quantitative RPR) and the Chembio DPP Syphilis Screen and Confirm RDT. We calculated the sensitivity and specificity of the RDT as compared to gold standard serology. The sensitivity of the RDT against TPPA was 58.5% and the specificity was 97.6%. The sensitivity of the RDT against RPR was 41.7% and the specificity was 95.2%. The sensitivity of the DPP was strongly related to the RPR titre with a sensitivity of 92.0% for an RPR titre of >1/16. Wider access to DPP testing would improve our understanding of worldwide yaws case reporting and the test may play a key role in assessing patients presenting with yaws like lesions in a post-mass drug administration (MDA) setting.

Yaws: Rebound of a forgotten disease

“…This study showed a lower sensitivity and specificity compared to the only prior evaluation of this assay [27], suggesting that the test is most useful for confirmation in patients with highly active clinical disease [26]. This rapid screening test does not perform as well in patients with latent disease nor useful in areas with low prevalence [26]. The search for a cost-effective rapid screening test in asymptomatic patients remains to be seen, however, does serve a useful function in post-mass drug administration monitoring.…”

“…The sensitivity of the ChemBio DPP syphilis screen was correlated to higher RPR titers, having a sensitivity of 92.0% for an RPR titer of >1:16. This study showed a lower sensitivity and specificity compared to the only prior evaluation of this assay [27], suggesting that the test is most useful for confirmation in patients with highly active clinical disease [26]. This rapid screening test does not perform as well in patients with latent disease nor useful in areas with low prevalence [26].…”

“…The sensitivity and specificity of the RDT against TPPA was 58.5% and 97.6%, respectively. The sensitivity and specificity of the RDT against RPR was 41.7% and 95.2%, respectively [26]. The sensitivity of the ChemBio DPP syphilis screen was correlated to higher RPR titers, having a sensitivity of 92.0% for an RPR titer of >1:16.…”

New Diagnostics for Yaws

“…Interest in yaws has been revived by the finding that azithromycin is a highly effective treatment of both primary and secondary yaws 2. Clinical diagnosis alone of primary yaws is unreliable, but a point-of-care test has been shown to be of value 3. This test provides a result analogous to a T. pallidum particle agglutination assay (Figure 2

Figure 2.Combined treponemal and nontreponemal rapid diagnostic test for yaws.

, line 1) and a rapid plasma reagin (RPR) assay (Figure 2, line 2).…”

Yaws Eradication — A Goal Finally within Reach

“…Progress toward the elimination of transmission could be monitored by means of point-of-care serologic surveys for latent yaws in children. 4 Finally, as with mass drugadministration programs for controlling and eliminating other infectious diseases, maintaining high levels of community participation in treatment and monitoring will be essential. Azithromycin uptake by 80% or more of eligible community participants, as Mitjà et al report in Papua New Guinea, with continued targeted community treatment will be critical if local elimination and, ultimately, global eradication of yaws are finally to be realized.…”