From the Laboratory to the Field: Assessing the Usability of the NTDscope in the Tropical Rainforest Region of Gabon

In regions where Loa loa is coendemic with lymphatic filariasis and onchocerciasis, mass drug administration of ivermectin has posed a risk for serious adverse reactions in individuals with high microfilarial loads. To overcome this problem, easy-to-use point-of-care diagnostic tools are crucial for identifying individuals at risk in population-based control programs. The NTDscope is a device that uses smartphone components for video microscopy and may support decentralized L. loa microfilariae screening under field conditions. This study evaluated the usability and operational feasibility of the NTDscope during population-based screening in a rural setting. A total of 200 adults were screened and 187 adults were enrolled locally by six trained health care workers with no experience using the device. From blood collection to automated analysis, the process was assessed to evaluate usability and identify potential challenges in field deployment. The device was well accepted by health care workers and participants because of its intuitive interface, portability, and rapid result output. Operational challenges included environmental factors and minor technical limitations. Nonetheless, the device performed reliably in the field without reliance on internet connectivity or electricity and required minimal training. Feedback highlighted the need for improved heat management, optimized error recognition, and enhanced data security. The NTDscope proved highly usable in low-resource settings where infection with L. loa is most endemic and offers significant potential for supporting large-scale treatment programs in L. loa-coendemic regions. Although this study focused on field usability, future research should evaluate the implementation in the frame of large-scale treatment.