A Digital CRISPR-based Method for the Rapid Detection and Absolute Quantification of Viral Nucleic Acids

Quantitative real-time PCR and CRISPR-based methods detect SARS-CoV-2 in 1 hour but do not allow for the absolute quantification of virus particles, which could reduce inter-lab variability and accelerate research. The 4-hour reaction time of the existing digital PCR-based method for absolute virus quantification is too long for widespread application. We report a RApid DIgital Crispr Approach (RADICA) for the absolute quantification of SARS-CoV-2 DNA and Epstein–Barr virus DNA in human samples that yields results within 1 hour. For validation, we compared RADICA to digital PCR for quantifying synthetic SARS-CoV-2 DNA and Epstein–Barr viral DNA. RADICA allows absolute quantification of DNA with a dynamic range from 0.6 to 2027 copies/µL (R 2 value > 0.98), without cross-reactivity on similar virus or human background DNA. Thus, RADICA can accurately detect and quantify nucleic acid in 1h without thermal cycling, providing a 4-fold faster alternative to digital PCR-based virus detection.