Most of the patient samples are negative

When there are many patient samples to be tested at once

A pandemic of COVID-19 is spreading across the world, but we don't have enough test kits to track who is and is not infected.Transitioning from a one-at-a-time testing scheme to a multiplexed assay can test as many as 10x more people with our current stock of test kits.Many testing facilities don't have the robotic liquid handlers to perform complex multiplexing, but any laboratory can carry out a paper based origami assay to get many of the benefits of multiplexing.Try for yourself with a small interactive game Multiplexing means that we strategically mix samples together before we test them as shown schematically below:In this small assay, 6 patient samples (1-6) are tested with only 4 assays (A-D). Each patient sample is split between two assays, and each assay contains samples from 3 different patients. This mixing process is called multiplexing. If any patient sample is positive, then the assay returns a positive result. The assay results are decoded by identifying which patent samples were present in all of the positive assays. Multiplexing works best for "needle in a haystack" problems meaning when:For the small example above we only test 6 patient samples with 4 assays, but larger designs such as the XL can test 600 patient samples in only 60 assays. See the full list of origami assay designs here.