A smartphone dongle for diagnosis of infectious diseases at the point of care

A smartphone accessory can perform a point-of-care test that simultaneously detects three infectious disease markers from fingerprick whole blood in 15 min, as operated by health care workers trained on a software app. Dongle + app = mobile test for sexually transmitted diseases There are thousands of health-related “apps” for smartphones, from tracking sleep patterns to recording heart rate to logging caloric intake. The power of such apps in connecting resource-limited communities to health care workers and, in turn, to proper and immediate care is now emerging. In this issue, Laksanasopin and colleagues describe a microfluidic-based diagnostic test for HIV and syphilis that attaches to (and is powered by) the iPod’s headphone jack. The mobile test also comes complete with an easy-to-use app, flashing test results on-screen in under 15 min. The test is based on the standard immunoassay but uses gold-labeled antibodies to detect HIV and syphilis antigens in only 2 μl of whole blood, and then silver reagents to amplify the resulting signal. The authors deployed the dongle in Rwanda, testing its sensitivity and specificity on 96 patients. Evaluated side by side with the gold standard tests for HIV and syphilis, the dongle produced results with a sensitivity and specificity needed for making treatment decisions in the field. In a survey, a vast majority of patients reported satisfaction with dongle performance. After a few next-generation tweaks, including reducing the size of the dongle, the entire diagnostic package is ready for adoption in resource-poor clinics and communities, to improve detection of HIV and syphilis and empower health care workers to administer timely and appropriate treatments. This work demonstrates that a full laboratory-quality immunoassay can be run on a smartphone accessory. This low-cost dongle replicates all mechanical, optical, and electronic functions of a laboratory-based enzyme-linked immunosorbent assay (ELISA) without requiring any stored energy; all necessary power is drawn from a smartphone. Rwandan health care workers used the dongle to test whole blood obtained via fingerprick from 96 patients enrolling into care at prevention of mother-to-child transmission clinics or voluntary counseling and testing centers. The dongle performed a triplexed immunoassay not currently available in a single test format: HIV antibody, treponemal-specific antibody for syphilis, and nontreponemal antibody for active syphilis infection. In a blinded experiment, health care workers obtained diagnostic results in 15 min from our triplex test that rivaled the gold standard of laboratory-based HIV ELISA and rapid plasma reagin (a screening test for syphilis), with sensitivity of 92 to 100% and specificity of 79 to 100%, consistent with needs of current clinical algorithms. Patient preference for the dongle was 97% compared to laboratory-based tests, with most pointing to the convenience of obtaining quick results with a single fingerprick. This work suggests that coupling microfluidics with recent advances in consumer electronics can make certain laboratory-based diagnostics accessible to almost any population with access to smartphones.