A multi-site pilot study of the deployment of cholera rapid diagnostic tests in the Democratic Republic of the Congo
Study design
Observational, mixed-methods study.
Context
Although extensive work on defining the theoretical basis of potential sampling schemes to estimate incidence has been done by the GTFCC, the practical deployment strategies for RDTs to support incidence measurement in field conditions require further refinement. First, after RDT deployment to the health facilities the respective people must be trained in the use of RDT and interpretation of the result for surveillance. For example, a field-applicable method is required to identify the scaling up of the RDT positivity rate in a sample of suspected cases to incidence estimates for all suspected cases and correcting for sensitivity and specificity. Before a successful integration of RDT into routine surveillance, more research on different strategies and their implementation is necessary for different scenarios. Moreover, the ideal sampling strategy must be adaptable to field conditions, based on the most commonly used RDTs. Furthermore they should be implemented by MoH staff without much supervision and follow-up in cholera outbreak settings with limited resources. Hence, the study will contribute to further refine the use of RDTs for cholera surveillance with a strong focus on the implementation in real world conditions.
Our role
Coordination of the study
Partners
- Ministry of Health of the DRC
- GAVI
Objective
- Assess the performance and feasibility of different cholera RDTs and their implementation into new surveillance strategies under a variety of real-world deployment conditions.
- Derive and compare estimates of the true clinical incidence of cholera based on RDTs using different sampling schemes.
First Results
All RDTs reached similar sensitivity (76%-81%) and SD Bioline highest specificity (87%, 95% CI, 80%-92%), which was significantly higher compared to Crystal VCO1. Enrichment reduced sensitivity significantly (SD Bioline and Crystal VCO1) and increased specificity (significantly only for Crystal VCO1).
The integration of RDTs into the surveillance system in line with the new GTFCC surveillance guidelines has been evaluated under real-life conditions.
In high-incidence areas, the application of this sampling scheme, i.e. testing the first 3 cases per day per CTC, enables accurate incidence estimates to be obtained, and saves up to half the number of RDTs.
In terms of surveillance, a probable cholera epidemic was correctly identified using the GTFCC threshold, with minimal involvement of the study team in DRC and Niger.
Conclusion / Impact
RDTs are an essential tool to improve cholera surveillance, particularly for rapid outbreak detection and monitoring. The new RDT based threshold proved to be a valuable tool for independent detection and for monitoring, a sampling scheme saves RDTs and still provides robust incidence estimates. However, providing RDTs to cholera affected countries is not enough, only with regular training and supervision, solid RDT data can be obtained.
