The human treponematoses comprise venereal syphilis and the three non-venereal or endemic treponematoses yaws, bejel, and pinta[1]. Syphilis, caused by Treponema pallidum subsp. pallidum, remains an important cause of both morbidity and mortality worldwide and remains one of the major preventable causes of stillbirth globally [2]. Stillbirths and neonatal death due to mother-to-child transmission of syphilis are almost entirely preventable through appropriate screening and treatment of pregnant women during antenatal care[3,4]; this intervention has been shown to be highly cost-effective [5], but access to syphilis testing is a barrier to implementation in many settings[6,7].

Yaws, caused by T. p. subsp. pertenue is the most common of the endemic treponematoses[1]. Although its aetiological agent is closely related to T. p. subsp. pallidum, yaws is transmitted by non-sexual skin to skin contact affects children living in poor, rural communities in the tropics, where the ambient humidity is high[8]. In 2012, the World Health Organization (WHO) launched a renewed plan to eradicate yaws globally by 2020 using community mass treatment with single dose azithromycin. Currently, when submitting data to WHO, most countries report clinically suspected cases without laboratory confirmation, but clinical diagnosis may be inaccurate, with less than 50% of phenotypically consistent cases confirmed serologically in some studies [9,10]. The development and validation of appropriate point-of-care diagnostics for use in yaws eradication efforts has been highlighted as a research priority[11], and would allow strengthening of national yaws surveillance programmes and accurate reporting of cases.

Serological assays remain the most common diagnostic method for all treponemal infections. Importantly, none of the currently available assays is able to differentiate between infection with syphilis and infection with any of the endemic treponematoses[12]. Standard serological testing consists of both a treponemal specific test, such as the Treponema pallidum particle agglutination assay (TPPA), combined with a non-treponemal test, such as the Rapid Plasma Reagin (RPR) assay. Treponemal tests are highly specific but generally remain positive for life following infection. Non-treponemal tests are less specific but reflect disease activity more accurately, and their titres fall following successful treatment. Testing therefore requires both assays to give an interpretable result.

Whilst traditional serological tests are relatively straightforward to perform, they require a cold chain and electricity, denying access to testing to those living in many remote communities. Point-of-care tests (POCTs) allow testing without further development of infrastructure in populations where routine laboratory facilities are not available. A large number of syphilis POCTs meeting the ASSURED criteria[13] have been developed [6] but the majority of commercially available tests include only a treponemal line. Although these tests allow identification of individuals who have been exposed to treponemal infection, they cannot distinguish between current and previous, successfully treated infection. In the antenatal setting, this results in the unnecessary treatment of women with previously treated syphilis; in yaws eradication programmes it represents a barrier to accurately assessing ongoing transmission following community mass treatment.

A single commercially available test, the Dual Path Platform (DPP-POCT) Syphilis Screen and Confirm test kit (Chembio, Medford, NY, USA) provides both a “treponemal” result (analogous to a TPPA assay) and a “non-treponemal” result (analogous to a qualitative RPR assay)[14], and can therefore distinguish between current and past infection. A number of studies and a meta-analysis have demonstrated that the test has a good sensitivity and specificity for the diagnosis but there have not been any evaluations of implementation of the test in a real world setting[15–19].

Alongside the test’s performance characteristics assessed through diagnostic evaluation, it is important to consider broader issues when rolling out a POCT. Adequate training and quality control (QC) steps must be developed, and both health-care workers and patients may require additional education about the role of POCTs in making a diagnosis. Experience with malaria POCT roll-out in sub-Saharan Africa has demonstrated that both healthcare worker and patient beliefs significantly influence the utilisation and interpretation of POCTs and may play a major role in shaping their use in real-world settings[20,21].

The Solomon Islands reports the third most cases of yaws in the world annually[8], after Ghana and Papua New Guinea. Recent ANC surveys have also show a high prevalence of syphilis[22]. Diagnostic testing in the Solomon Islands is limited to hospital laboratories. As a result testing for syphilis in rural clinics relies on sending tests away to a local hospital, whilst most cases of yaws are never confirmed serologically. These gaps in current diagnostic test provision highlight a potential role for the DPP-POCT in the Solomon Islands to improve access to testing for both yaws and syphilis. We conducted a qualitative study evaluating healthcare worker and patient perceptions of using a syphilis/yaws POCT in clinics in the East Malaita region of Malaita province in the Solomon Islands.

Over the study period approximately 500 DPP-POCTs were used across the study sites. We interviewed a total of 20 health care workers, 12 at the one month time point post training and a further eight healthcare workers at the six month time point post training. We additionally interviewed four patients who had been tested using the DPP-POCT.

In this study we provide the first real-world evaluation of the acceptability of the DPP-POCT in routine health care settings, in a country co-endemic for yaws and syphilis. Whilst a number of evaluations have been conducted of the analytic performance of the DPP-POCT[14,18,19], no previous studies have addressed factors affecting its real-world roll-out. Our data highlight the ability of these tests to improve access to diagnostics for patients in remote communities, and the receptiveness to the test of healthcare workers and patients. Our findings also highlight lessons that can be learnt in guiding roll-out of the DPP-POCT to support both yaws and syphilis control programmes.

The majority of nurses reported a high level of trust in the test, and both patients and nurses recognised the benefits of making diagnostic testing available in primary health facilities without recourse to a hospital laboratory. The test was generally reported to be easy to perform based on the training received in the study and despite the relatively long time required to obtain a result, nurses reported the test could be integrated into clinical workflows. Previous studies of the roll-out of rapid syphilis tests in other settings have also demonstrated an overall high level of acceptability and feasibility [23]. In line with our findings, these studies highlighted the potential value of reducing travel time to access tests and the ability to offer same day treatment and testing to patients.

In the current study, many health care workers drew parallels between their experience of the DPP-POCT and their previous experience with malaria RDTs. Whilst familiarity with RDTs was clearly advantageous, it also highlighted how lack of confidence in one test kit could affect the roll-out of a second, unrelated, test kit. Adoption of RDTs for the diagnosis of malaria has not always translated into anticipated reductions in the number of patients treated for malaria in the real world[24]. Studies of RDT roll-out programmes have highlighted the complex interplay between patient and clinician expectations that drives how clinicians interact with, utilise and interpret RDTs[25]. Taking account of these interactions and building more sophisticated training and support packages are important facilitators for successful adoption of RDTs[21]. Our data might inform a refined DPP-POCT training package.

There are a number of limitations to this study. Firstly, we focused on a relatively small number of clinics over a fairly limited timeframe. This reduced our ability to consider the impact of broader health systems factors that may influence the feasibility of rolling out the DPP-POCT. Previous studies on syphilis RDTs have highlighted the importance of supply chain and quality control monitoring systems in maintaining long term effectiveness of RDT scale-up at a national level[23]. These cross-cutting issues would be important to consider in the context of a broader programmatic scale up of the DPP-POCT. Second, we did not consider issues around the cost of introducing the test kit, either from the perspective of eliminating mother-to-child-transmission of syphilis or from the perspective of supporting yaws eradication. Whilst antenatal screening for syphilis is considered a highly cost-effective intervention[5], the optimal strategy depends on the prevalence of syphilis and the cost of the test kits. In many situations, use of a treponemal-only rapid syphilis test is more cost effective, albeit at the cost of over-treatment[5]. Cost-effectiveness studies on the use of RDTs for yaws have advocated that a two stage screening process, an initial treponemal-only test followed by a DPP-POCT if positive, is more cost-effective, given the current cost of the DPP-POCT (Fitzpatrick REF–accepted PLOS NTDs).

This is the first study to assess the acceptability of rolling out the DPP-POCT in a routine health care setting. We highlight the potential added value to both patient and healthcare workers that can be provided by positioning these tests at the primary health care level. Longer term and larger evaluations of DPP-POCT would be valuable to assess the impact and cost-effectiveness of scaling up access to the DPP-POCT on the management of syphilis and yaws.