A portable device that detects measles and rubella antibodies in about 35 minutes has potential applications in both remote and conventional labs settings. Such a technology could expedite testing in developing countries where these diseases persist but access to laboratory resources are scarce.
Developers of the Measles-Rubella Box (MR Box) compared its performance against more conventional serosurvey assays and published their findings in Science Translational Medicine. “We demonstrated this technology for its use in remote settings, where sending tests to a centralized laboratory is not an option. However, we think this technology could also be useful for traditional laboratories or even in a distributed (versus centralized) testing model,” Darius Rackus, a lead author of the STM article, told CLN Stat.
Clinical labs routinely batch samples and run them together. However, because the MR Box only has modest throughput (4 tests/cartridge), labs that were to use it would not have to wait for many samples before running a test. “This could be particularly useful in an established lab for performing less common tests that are infrequently performed,” Rackus said.
The MR Box uses a pinprick volume of blood on a microfluidic cartridge to test for immunity to measles and rubella. “Our cartridge relies on digital microfluidics. This is a technique for moving small droplets on an array of electrodes,” Rackus explained. “We apply voltages to the electrodes to move droplets of samples and reagents around. This is very similar to how a statically charged comb or balloon can be used to bend water.”
MR Box is a bead-based chemiluminescent enzyme-linked immunosorbent assay that uses microscopic magnetic beads that have the measles or rubella virus attached to them. “We mix the blood with these beads, which extract any anti-measles or anti-rubella antibodies from the blood. We then use another antibody to label the captured antibody,” Rackus explained. An enzyme connected to this label catalyses a reaction that produces light that the user can measure. “The amount of light is proportional to the concentration of the antibody we are trying to measure,” he added.
Rackus and his colleagues collected blood samples from 144 children and caregivers in a refugee camp in Kenya to test this device in the field. They found that MR Box performed reasonably well compared to the reference tests, with a measles test sensitivity and specificity of 86% and 80%, respectively, and a rubella test sensitivity and specificity of 81% and 91%, respectively. While the results weren’t perfect, “this was the first time taking the technology platform out of the lab. We are very excited by these results,” Rackus said.
Through their field trial, investigators have identified next steps for further developing MR Box, such as building a battery-powered system and advancing the technology so that a non-expert user could run an assay. “For our trial in Kenya, we sent a team of four students and postdocs from our lab to perform the assays. It would be ideal if we could deliver a box and cartridges to local healthcare workers, train them, and have them run the assays without our input,” said Rackus. “This is a huge engineering challenge, but we are eagerly working on it and have plans to do a trial with local users in South America.”