Diagnostic Tools for Human African Trypanosomiasis Elimination and Clinical Trials: WP2 Passive Case Detection

In the last decade, the prevalence of Trypanosoma brucei gambiense human African trypanosomiasis (HAT) has fallen and HAT has been targeted for elimination. At low disease prevalence, integration of case finding into routine activities of peripheral health centres becomes crucial. However, HAT case detection by the peripheral health system with limited resources requires adapted diagnostic tests and test algorithms.

The objective of the DiTECT-HAT-WP2 study is to determine the diagnostic performance and cost of rapid diagnostic tests (RDTs) performed on clinical suspects in peripheral health centres, whether or not followed by serological and/or molecular tests on filter paper done at regional reference centres.

The DiTECT-HAT-WP2 study will be conducted in centres for diagnosis and treatment and in sites for serological screening in Guinea, Côte d'Ivoire and DR Congo. In these centres and sites, clinical suspects will be tested with several commercially available RDTs for HAT. Clinical suspects with at least 1 RDT positive result, will 1° undergo parasitological examination and 2° blood collection on filter paper for reference analysis in trypanolysis, LAMP, ELISA and real-time PCR in the regional reference laboratory. If the reference laboratory tests and parasitological examinations are all negative, the suspect is informed and considered free of HAT. If at least 1 reference test is positive, parasitological examinations are repeated at least twice at three months interval, unless trypanosomes are detected. In order to assess the sensitivity, specificity, Positive Predictive Values and Negative Predictive Values of each assay in these multiple populations, the data from the multiple assays in the 3 countries will be used in a Bayesian formulation of the Hui-Walter latent class model, to estimate the assay performances in the absence of a gold standard. As we will collect full cost information for the different algorithms, we will, in addition to estimating the diagnostic effectiveness of the assay, be able to estimate the cost of each assay in each setting, and rank this jointly with assay performance.

The results will enable us to propose cost-effective test algorithms to detect HAT, adapted to peripheral health centres. Algorithms with high positive predictive values might allow test-and-treat scenarios without the need for complicated parasitological confirmations, once safe oral easy to use drugs become available to treat HAT.