Point-of-care COVID-19 assays that are more sensitive than the current RT-PCR (reverse transcription polymerase chain reaction) gold standard assay are needed to improve disease control efforts. We describe the development of a portable, ultrasensitive saliva-based COVID-19 assay with a 15-min sample-to-answer time that does not require RNA isolation or laboratory equipment. This assay uses CRISPR-Cas12a activity to enhance viral amplicon signal, which is stimulated by the laser diode of a smartphone-based fluorescence microscope device. This device robustly quantified viral load over a broad linear range (1 to 105 copies/μl) and exhibited a limit of detection (0.38 copies/μl) below that of the RT-PCR reference assay. CRISPR-read SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) RNA levels were similar in patient saliva and nasal swabs, and viral loads measured by RT-PCR and the smartphone-read CRISPR assay demonstrated good correlation, supporting the potential use of this portable assay for saliva-based point-of-care COVID-19 diagnosis.
Read full text: A smartphone-read ultrasensitive and quantitative saliva test for COVID-19. BO NING, TAO YU, SHENGWEI ZHANG, ZHEN HUANG, DI TIAN, ZHEN LIN, ALEX NIU, NADIA GOLDEN, KRYSTLE HENSLEY, BREANNA THREETON, CHRISTOPHER J. LYON, XIAO-MING YIN, CHAD J. ROY, NAKHLE S. SABA, JAY RAPPAPORT, QINGSHAN WEI, TONY Y. HU SCIENCE ADVANCES, 08 JAN 2021 : EABE3703