Equipmentless point-of-care testing of dengue antibodies using ELISA and smartphones

Infections with the dengue virus affect more than 100 million people every year. The infected can present a mild form of the disease or a severe form, which can, eventually, lead to death. Dengue prevails in tropical and subtropical regions, although increased incidence has been observed in the last years in tempered climates. Vaccines are available but testing for previous infection is often required prior to application. Commercially available ELISA and rapid tests for the diagnosis of dengue IgG do not fulfill individually the performance required by control agencies. In this context, rapid, simple and decentralized point-of-care testing (POCT) is highly desirable. However, POCT approaches available usually offer expensive solutions, often due to the complex complementary hardware required. In this article, an equipmentless system based on a commercial ELISA kit and a smartphone is developed for POCT of dengue antibodies. A customized app provides guiding, optical reading, result reporting and connectivity. The reading method employes an algorithm which requires no external information, other than the available on the digital images from the smartphone camera, to classify samples into positives, negatives or indeterminates. The full system operation, from sample extraction to result reporting, was tested in a low resource medical facility with real patients (n = 26). After comparison with an ELISA reader, a Cohen's κ coefficient of 0.92 was obtained, showing very good agreement between both methods. These results show that it is possible to perform ELISA with no specific equipment, bringing massive testing at low resource facilities one step closer.